It's fine, I just think that more people will bite if you have an example of your artwork. It could also serve as practice before the game jam.
Nice! I wasn't planning on participating since I'm working on releasing my game. I could possibly be open to do the game jam at that time and I will have a better idea by August 20th. If you don't have a partner/team by that time I'll be willing to work with you. If you would like to collab, my email is chukobyte@gmail.com.