Can Lego soccer (football) parts be used for anything other than soccer?
The green parts are great to make a green smooth field, which is kinda obvious. Landscaping is one usage, and if you find it too uniform, don't forget you can cover some areas with additionnal hills or whatever. The Technic hole in there can come handy as you can easily attach something in it. Since it'll rotate freely, your added decoration can even be placed at an angle. Trees come to mind too: you can attach them to the Technic hole too, and maybe fill the green curved area with brown 1x1 round plates to symbolize earth.

The fact that it's green isn't always the most important aspect; sometimes you'll just need a big horizontal flat surface just for its flatness. I've used some of these parts (tan ones) to create a flat layer udner a SNOT river (basically a wall of blue bricks on the side). Doing that with 2x2 tiles would have been cumbersome, and more importantly I could use parts which I usually have no use for. In my specific case, the fact that they can be attached on duplo bricks was a plus. 

The minifig stands aren't that much useful, but the spring in them means you can hope to build interesting mechanisms, especially projectile ones. Have a look at the instructions of set 7020 — Army of Vikings with Heavy Artillery Wagon, the designer of that set did an excellent missile launcher with it.

Don't get me started on what to do with the soccer balls.