Boy oh boy, has it been that long since I've seen your sprites?? I feel like it has. Keep up with the work on it! Getting pretty good with it~ If you ever need suggestions or ideas, you know who you can hit up for em!
I mean, back when I used to do spriting for this project, I started with sprite edits myself (though I never went past that since I didn't have the capacity to do so...). I'm sure a lot of people started with sprite edits before moving on from there. In fact, a lot of the Sangues you see here (and Midnight Blisses and Shocks) for the older stuff came from sprites already from the characters.
I'd go Lilith Treatment personally, just to play off of her own breast envy she has (yes, that's a legit thing she's got), but stomach or feet can work just as well (and are probably the only other ones that'd work well honestly).
The Beach one probably is the best one of the 3, though the Sentai one is kinda hilarious. I mean, outside of artwork for her, there's always something that can fit nicely for specific characters. Just...have to figure out what would is the problem. @_@ Some are much easier to do than others though *Looks at Athena*.