Illustration for a Dino-Exhibition

I need an very realistic illustration for a upcoming Dino exhibition. Size A3 or A2 by 300dpi. Please see attached photo for a similiar work. Kind of wild background with 2 or 3 Dinos in front. Logo will be placed on it by myself. Need Photoshop files (CS6) with all layers. All objects have to be drawn in full on separate layers even they are overlayed by other objects, because usually I have to move them slightly to place logo and some text on it. Only self drawn work is accepted. DON't USE stock graphics! Please deliver a sketch first, not ready made artworks. I am a reseller mostly working for circuses. Make a good price and provide great artworks and there is more to come!