this isn't really vital to anything, just out of curiosity:

I created a 10k billboard for my pet profile / css shop and between the time of uploading the billboard image and it being approved, I created a new css. I think it looks gr8 and would like to advertise it. is it possible to update the image of the active billboard? I'm not sure how long it takes to go through 10k views..

I would suggest sending in a ticket. I'm pretty sure there's no way to change it on your own.

Alternatively, the 10k billboards are cheap enough that it might be worthwhile to pause your current billboard and just make a new one.