How about orange as accent rather than theme? Gray blue goes great with orange, you could have a blinds, bunting, bedding, even paint his chest of drawers or toy box... Birds egg from Dulux is a lovely blue with a hint of grey and I'm planning on using it in DS2's room, and accenting with orange and bright blue.
DS2 has bright orange (and I mean bright!) and white on alternate walls. He had a lime green wardrobe from ikea (the kids one), a white Billy bookcase and cheeky monkey cot bed bedding from argos as well as blue/green/orange animal bedding from Asda. He still has his jungle curtains from when it was a nursery (we haven't got round to replacing them!). On the wall above his bed we have a hanging monkey wall sticker. All sounds a bit mish mashed but works really well.
then something else bright on the walls. When going "unusual" I've always gone for easy to replace rather than the slightly harder to cover bright walls. Non creative tho!! If he's in a single, there are some cheep orange solutions while you think further!
I wouldn't do a hungry caterpillar theme, he will see that as babyish very quickly. Just do bright colours and I think it's enough, no need to utterly theme it. My boys have a broadly space theme but it is not in your face.
We did burnt orange and lime green on opposing walls in my toddler DD's bedroom. With cream and lime green curtains (ikea) and lime green toddler table and chairs (ikea) it looks good if I do say so myself
DS has requested orange in his new bedroom. I'm not particularly creative and am trying to work out how I can incorporate this when he doesn't want dinosaurs, outer space, jungle etc. He likes the Very Hungry Caterpillar but I'm not too sure if this is a bit young for him, he's 3.5. I could easily incorporate one orange wall into this. I have searched high and low for other bedding with orange in it without much luck - not really into the really commercial stuff. Anyone creative out there that can help please?