I create these images. They are called vectors.
I described the vector vs raster images before and gave a brief overview of the process: Generally speaking, there are two types of digital images: raster and vector. Most images you see are raster. They are made of pixels. The more pixels, the higher resolution. Zoom into any raster image and you can see the individual pixels. When you change the size of the image, a computer just resizes those pixels. That is why most enlarged images appear fuzzy.
Vectors are different. They are "lossless." That means they are saved in smooth lines. If you zoom in very close to a vector, the line remains smooth. Vectors are characterized by clean, solid lines. They don't have gradients. For this reason, they are good choice for logos.
Here is where things get a little a complicated. The files I posted are raster images exported from vector files. I create a vector illustration but to post it, I have to export it as a bitmap. So you are truly seeing a raster image of the vector.
The type of image I create is like a rotoscope (think Scanner Darkly). They are vector traces of photographs. Their complexity depends on the detail and the number of discreet colors used.
There are filters that can create vector images. For example Vector Magic. I use filters to help but ultimately draw almost every image line by hand. A design done by hand will look better than a filter. These can be very labor intensive.
For example, there is a specific rotoscope filter that was used for A Scanner Darkley (it is not available for purchase). Anyway, even with that incredible digital tool, it still took 50 artists over 500 hours to create that film.
Here is a tutorial from a very talented artist:
He doesn't use any filters and the results are extremely impressive.
Hope that helps. I have been working on Christmas projects and haven't had time to create any new wallpapers. If I make anything new, I'll be sure to post.