Hi - you have a few choices on paint colours - you could use blue, red and grey i.e. you could have a feature wall in a dark blue and the others red or vice versa or perhaps the feature wall a dark blue and the rest a silver grey, or you could have two red and two blue walls, or you could have all the walls silver grey - and then put a few wall decals on. One giant wall decal on your feature wall would look great :) although these are quite pricey.

If you went with the above colours - I would choose something the same or similar to these colours:)

http://www.benjaminmoore.com/en-us/paint...

http://www.benjaminmoore.com/en-us/paint...

http://www.benjaminmoore.com/en-us/paint...

This bedding would look nice for your Marvel Themed Room and would go with the colours above for your walls no matter what colourway you chose for your walls :)

http://www.walmart.com/ip/Mainstays-Stri...

And... these Giant Murals would look on your wall - I would perhaps just choose one really large one and if you want anymore just use a few small ones

http://www.amazon.com/gp/search/?ie=UTF8...

http://www.amazon.com/gp/product/B00CMYS...

http://www.amazon.com/Superman-XL-Wall-M...

Small wall decals

http://www.amazon.com/s/ref=nb_sb_ss_i_0...

This would be cool for your room :)

http://www.amazon.com/Bratz-World-London...

You will find quite a lot of ideas on here for your room :)

http://kidsthemebedrooms.com/superheroes...

Hope the above helps and good luck with your room :)