They will be seen regularly by hundreds (soon to be thousands), so your art will be high profile with lots of notoriety and kudos to come your way I'm also happy to kick-in a little $ too, if required.
Design brief: Obviously be representative of site, following the colour scheme etc. and of course display the site logo within (send me a conversation if you want a high-res version). But I primarily leave it up to the talent and imagination of those with far more graphic ability than me to see what you come up with.
1. Portrait - 1536 x 2048 PNG. Splash screen may be resized, with edges being slightly cut-off.
2. Landscape - 2048 x 1536 24bit. Splash screen may be resized, with edges being slightly cut-off.