Ultimate Apocalypse is the one I play too. It's a little tricky to install and you'll need a decent computer to play it to its full potential (the Sisters have insanely high-res textures, clearly the creators were predominantly guys

), especially if you want to go online, but it's worth it. I'd recommend you play the standard game long enough to get comfortable with all the controls and army play styles, if you haven't already, before moving onto
UA though as it shifts things about a lot. However this is a small downside when you consider that it adds titans, new units and Tyranids, as well as Grey Knights and Daemons (although they're temporarily unavailable while it's updated).
Aside from that I don't know any others specific to Dark Eldar and Sisters.
UA makes both of them so much better. I suppose you could search for maps themed to their armies?