The method used to make the background for today's image is through the use of free brushes found on the web. Do a Google search Photoshop/Brushes/"Topic". Where "topic" is whatever sort of brushes you might be looking for. There are a couple "gotchas" when browsing through the huge number of brush websites. One would be paid brush sets. I see somebody charging for brushes, textures, actions, etc. I just keep on walking. I don't begrudge anyone trying to make a buck on the work they've put into creating something, it's just that there's a lot of folks who do it for the pride rather than the profit. Some of the free stuff isn't that great, but I've seen some things people were charging for that wasn't up to snuff either. Second would be sites that would like attribution. I have nothing about those sites to disagree with. I think they deserve our support and a mention thanking them for their work and (if they ask) tossing a few bucks their way. Those sites typically have a notice that says "here ya go, have fun and please let people know where you got the ???". Some throw in "oh, by the way, if you can afford it, think about supporting the effort". If they include a method of getting them some money I'll pop for a couple bucks every couple months. They won't get rich off of what I send them, but if everyone who used their creations sent a little they could make a living (or at least have a lunch paid for by a grateful user). The third type of site is just plain free. They don't ask for any donations. They don't give an easy way to give a donation and they do it for the love of creating. These sites typically have the most junk but every once in a while you'll find a gem. With enough looking you can find more than a base amount's worth of what you're looking for to get you past "getting going".
To make the background for today's image it's just a series of Brushes on a series of Layers. Each time a pick a new Brush I put whatever it makes on a New Layer. If I take a Brush (B), use it more like a stamp, turn it, stamp again, flip it, stamp again, etc. I'll usually put it all on the same Layer if it's all the same color. Once I change colors it means (for me) a new Layer. So, new Brush or new color means adding a New Layer. I'll save the background out as a separate PSD file so if I want to use it again or start another background based off of the one I just made, it's no problem. I'll also bring the background into a new arrangement as a Layered file so I can add, subtract, alter the colors and play with the individual Layers depending on the content I'll be using it for.
Check by on Friday and I'll take a look at how I "doctored" the athlete's images to have them come in and out of the image.