Wow. That's a really sweet modification of Cap's costume. Anyway, what size do you want the picture to be? 1024x768? 1280x800? Something else? Be forewarned that the picture will become pixelated and/or blurry, because it's not very big...
Anytime you take a small picture and expand it to make it larger, pixelation/blurriness WILL happen. If you want a large, hi-res, hi-def picture (in other words, a large picture that actually looks good), the original pic needs to be scanned/created in a hi-res format. Best chance of getting a large, hi-res version of that pic is to go to the original site from which you got it and/or contact the creator of it to get it.