Some quick handy tips for when the voting comes live...
Try to see how the banner will look in place. Some look amazing on their own but don't look right when on the forum page.
Is it more of an advertising banner than an identifying/background banner?
Look at the colour scheme used. Does it fit with the blues/greys/whites of the forum or does it stick out like a sore thumb? Of course, some contrast can be a good thing but it should at least try to look like part of the design.
In this case, the banner should probably not be the most prominent thing on the screen (unlike when creating advertising banners). It should be a nice addition to finish off the header of the page and not something distracting.
Personally, I think the over use of plugins, stock photography and clipart should be frowned upon - but thats just personal opinion
Good luck everyone.