I want to introduce this web site to you. With your photos (from your personal computer or flickr), you can create collages from these photos and then as wallpapers so that you can put them up in your screen.
I tried it out.. I tried to create a 30 photos collage and hence upload 30 photos. There was however a bit of glitch when I upload and the collage came up to 29 photos. The next time I tried, I uploaded 31 photos and still 1 failed. But this time, I got the 30 photos I needed.
The results are vey good. You get a choice of 3 different resolutions, 800×600 or 1024×768 and 1280×800 which you can use for your PC.
Try it out !