By the way, the "Get a Holt" area at Scroll of Colors also, to the best of my knowledge, only features active Holts at the moment.
We have a couple of options that we recommend to folks who may be interested in River Twine, but don't feel like they can connect with a male character (or, any of the present adoptables, regardless of gender):
-- we have a "Reader Member" option, that allows folks to comment on the website, and also full access to our messageboards (for voting, and to participate in discussions). The other main perk of this is that should a character become adoptable (through a member leaving, or by other means), Reader Members are given a 1-week first crack at them, before they are announced as publicly available. Recently, Foxtail became adoptable, and one of our RMs snapped her up. So it's a good option for folks who are "waiting for" other adoptable options.
-- of course, we'd like folks to have a genuine interest in whichever character they adopt! But we do allow character-switching (depending on availability, of course). So if someone winds up adopting a character, but just can't "click", that does become an option. (While we'd like to see people doing art or fic for their own character, River Twine also encourages people to write stories and do art for others' characters, too. So, the character you adopt doesn't restrict what you can do.) We had a couple of members switch to some recently-available child characters, and we knew it wasn't because they didn't love the characters they had, it was just that the child characters appealed to them even more. So that's certainly one way for people to bide time waiting for other characters to become available. (We'll have more children able to be adopted next summer.)