I'm working on Opencart website with the Journal theme. Please see following links:
http://journal.digital-atelier.com/2/
http://journal.digital-atelier.com/3/
http://journal.digital-atelier.com/5/

As you may see, background plays an important role, so I really need to choose a neat one. The topic should be fitness, gym, workout, supplements or something else related to that. I've already browsed through a lot of wallpapers on Google, but couldn't find any appropriate ones. If possible, background should be in yellow or blue color (or a combination), which even hardens the choice since most of such wallpapers have white or black background, which is not really suitable for my case. Implying to the demo wallpapers from upper links, wallpaper should be rich, full of colors but not oversaturated.

It's a really tough topic, finding a good wallpaper for football, skiing or any other more popular sport would be a breeze. I've already considered on taking a nice blue background and putting fitness model on each side of it, but it would probably come out amateur. I'm just not that skilled in Photoshop.

My question is practically a request. I would be glad if you could provide me any ideas, advices, good links where such wallpapers/backgrounds can be found, maybe even some examples etc.? Thanks in advance .