Also another question (yeah I know sorry) -all of the girls' pictures currently show them naked. Is there a way to include a picture with an outfitted variant of a girl?
I give up and admit I'm not having much success with this. Could you please give a step by step explanation of how you got the pictures to show up in the game as they should (transparency and all)?
Don't worry about asking questions, the forum is there for that purpose.
1) There is a way. You can see in content/pic/girls/full that there are three folders (secretary/mistress/maid). Only a few slaves have these (mainly Isabella, and I think that's only when you have them assistant, but I could be wrong; the different outfits appear in the rule tab, in-game).
In the json/slaves folder, you can try to see what lines Isabella has that slave 1002 (for exemple) doesn't. It should be near the beginning (you can open the json file with notepad++). After some intuitive copy-pasting and tweaking from your part on 1002's json, you should now have a line that leads to the full/secretary (or maid+mistress) folder. Now you need to add the picture with the clothed slave, and when you'll have this girl as an assistant (needs devotion>3), boom, new outfits available.
Of course, we aren't in a sci-fi world where the computer generates drawings of the girl once you equip her with clothes in-game. So you'll have to keep your suspension of disbelief towards that.
2) You have paint.net? I'm not on my computer so I can't make proper screenshots to show you how to do it. I can do that that in about 18 hours. Or, you can take screenshots of what you tried, and I'll tell you what you did wrong.