Resurrecting this thread (I think I noticed it before, was interested, and had been waiting to see what others posted; also that was in my "still can't type" period)...
Some thoughts.
Tracing: I've certainly been an advocate for tracing as a learning exercise (when it's combined with other techniques), although I tend not to advocate that people post the results. But, if someone wants to post them, my feeling is that credit is always a must. (I'll touch on the idea of permission in a moment.) Not just credit, but saying that it's a tracing. On top of credit just being a good idea (you can never go wrong giving *too much* credit, only in giving too little), I just feel like it's important to let your audience know what they're looking at. I would guess that the reason for posting a tracing is that you want to show your audience what you did to customize it, or your coloring, or whatever -- that there's something you did to it that you want people to see. That's fine! I think it's just a very good idea to make sure that your audience doesn't think you did more than you did.
Referencing: I'm fine with people using referencing to help them figure out how to draw something. I do it all the time, too. I feel that referencing is the necessary stand-in for drawing-from-life (which is more the ideal, but impractical for most situations these days), and to be honest, I'd rather see folks look at some references to help them figure out how to get started with something they don't "know" yet (be it human/elf anatomy, or animals, or whatever), than to keep on producing things that make it obvious that they haven't ever looked at "the real thing" to see how it works, and thus, wind up perpetuating mistakes in their work.
I find referencing to be more of a grey area, in terms of when to give credit to others. For myself, it involves a lot more "rules of thumb", and I can totally understand why opinions and habits vary.
Part of it, for me, depends on the degree of copying/referencing. Am I just using a small piece of someone else's work to help me figure out how to do what I'm trying to do? (A hand; a leg; a face in profile.) Or am I looking at a large number of examples in order to create something that "fits in" with them, but isn't as easily said to be based on any one in particular? (For example: looking at a whole bunch of Wendy's "elves riding wolves" to figure out how to do the legs on the elves.) I tend not to feel it to be necessary to "footnote" a piece to that degree, although I think if it was something *particularly* tricky, I might indeed feel the need to alert my audience that the tricky bit of my piece owed something to this other artist figuring it out first (or, photographer documenting it). I've also certainly sometimes given blanket credit (such as indicating that I have used Monty Sloan's Wolf Photography site extensively for wolf refs).
Sometimes, I also feel that a level of referencing will be understood by a particular audience, and they will know anyway that I must have looked at references. In a way, I kind of put the entire "drawing ElfQuest elves" into that category. I *expect* my audience to know that I've looked at Wendy Pini's work, and am trying to do elves in her style! (I'm not trying to "fool" anyone into thinking that the way I draw elf ears is somehow original to me, you know?)
But, if I do a piece for which I rely on a large degree of copying of a referenced work (such as a full figure, or, like more than 50% of a figure), that's when I would start to feel it was necessary to point people to the original that I used as a reference. (An example of this in my gallery is "Starskimmer Reclining", in which 90% of the figure was based on a painting, so I point to that painting.) This is related to what I was saying above, about wanting my audience to know what they're looking at, and to appreciate the work I did (hey! check out how I was able to freehand that sucker!), while not getting fooled into thinking I did more than I actually did.
Permissions: as a fan artist, I recognize the fact that there's a difference between the way we interact (or, don't) with the pros, versus how we interact with other fans/amateurs. On the one hand, we have a lot more access to other fans. On the other hand, pro artists/photographers have good reasons to protect their copyrights. And on a third hand (...what?), we recognize that if fellow fans/amateurs aren't pros, then all we have in the fan community is our own reputation for our work; all we have is social capital, in other words, and it's important to respect that.
It is often impractical or impossible to obtain permission from a pro to use their art for tracing or for referencing. So, IMO, that can be why giving clear credit is important -- it's all you can do.
With fellow fans, especially ones within the same community you're posting in, you CAN ask permission beforehand to use their work in certain ways. By and large, people seem to know this -- at least, this community and the SoC seems to have the cultural habit of people asking permission before they color someone else's work, for example, and of course people are good about indicating who the artist was when they post the colored version. I would think this would pertain to tracing too. The question is how much it pertains, or should pertain, to referencing.
Me, I would still go by the practice I outlined above -- depends on the amount of referencing done. A hand? No. Figuring out how to do eyes or ears? Nah. A full or almost-entire figure or pose? Yeah, that's something where I'd at least give credit (and probably start off with a "I hope you don't mind if I use your piece as a ref" note), particularly if the referencing had helped me to figure out a "problem" that I was struggling with, because after all, if it was the other artist who'd solved the "problem", rather than me, it'd be good to indicate that.
Designs: while this wasn't mentioned, this is something I think about as well. Obviously, as EQ fan artists, we're all drawing on a known pool of original art (Wendy's and other EQ artists), which help to form the basis of our character designs. But each of us brings our own creativity to the table as well. I've starting trying to get into the habit of clearly indicating to people when I'm drawing someone else's character, whose design was done by someone else. (I was noticing that I was getting compliments from people for my costume designs, for example, and I wanted to be clear that actually, I'm NOT very creative about costume design, and some of the designs they were admiring were done by someone else.) So I think that can sometimes be a good idea as well.