@Maureen All the things you noticed are great! Those can definitely be something to pay attention to. When I say "theme" I was more so referring to what they are painting. What kind of subject matter is inspiration using?
Now, one thing to know is that there may not be a common theme that is obvious. That is ok too. But it's important to at least look for it. I'm trying to get you guys to look at your inspiration from different angels. Subject matter, character design, media, format, etc. We need to figure out why we are attracted to certain work. That way we can integrate that one thing into our work without taking everything from the artists we are looking at. Some artists I just love their line work, but don't really like the finished art per se. Mobius would be an example of this. I am not a huge fan of his finished art. I've never been too much of a sci-fi guy. But I LOVE his line work on some pieces (but not all). I love Lizbeth zwergers backgrounds and monocromatic work, but not her color work.
I try to analyze each artist I like and see what it is that really pulls me in. So any of the things you noticed on your inspiration could be what draws you to that work. Or maybe it's something else? You need to look hard and see what it is. : )