Banner?

I am making an InivisionFree RP Board myself, and it's almost done, save for a few explorable areas, addition of the rules to the board and..

THE DAMN BANNER.

What is the best banner size for InvisionFree boards?

For those curious, here is the link to the board:

Dark Crescent

Hmm~
Looks interestin'
What's it about?
And, in Off-topic, does it mean that IT isn't SFW, or that it IS SFW and the rest of the board isn't?
And, you said NFSW and not NSFW.
^.^
I'm such a grammar nag. :3

I think it seems pretty good.

But I need to know something...
1. Why do you need help with the banner? It seems alright...
2. What is it? Is it Ryuusie No Rockman?