I am working on making the facebook page for renshuu (http://www.facebook.com/renshuu.org) a bit more useful. Right now, there is a placeholder image, but I would love to have something in there that was directly tied to a)renshuu.org, or b)Japanese language learning.
Here is the official size of the image: Cover photos are 851 pixels wide and 315 pixels tall.
The best image (chosen by me) will get 6 months of free renshuu pro! Contest will finish at the end of June, although if participation is low, it might end earlier (with warning, of course)
I'm pretty good with photoshop and drawing in general. If you have something somewhat specific in mind, I'd be happy to work with you on making a banner!
(sorry this is such a late response)
If you still want a new one, please let me know :)
I mainly need image dimensions, and the focus of what you'd like in it.
Actually, got one right now that I'm quite pleased with, but I will keep your offer in mind for the future - if something comes around, I'll see if we can arrange something mutually beneficial :)