Bumping with an idea:
If anyone wants to try mixing TRAINER sprites, I compiled a list of all the main series trainers from bulbapedia, and culled out a few classes that don't have their own sprite (ie most of the actors without a special sprite) and will try to remove classes that don't have a 3rd-5th gen sprite, though I don't know how well trying to incorperate 3rd gen sprites is... either way, if anyone wants to try it, you can generate some numbers between 1 and 149 on
http://www.random.org/ and I can give you the corresponding trainers. If one doesn't have a useable sprite I'll cull it and give you the next one up.
I did this one just now and it's pretty difficult so I'd only recommend it for intermediate to advanced mixers.