There is a great description of making turns here on the MTMG site.
http://mtm2.com/~mtmg/Traxx/textures/custom.htmlI don't know of any sources of premade turns that you can just cut up this way, so assembling the turn initially is going to be up to you.
After you draw the lines for the turn, you can fill the areas with any good tiling texture you find on the Internet, there are tons of them available, mostly intended for web page backgrounds. Photographs are great source too, but you will need to make the part of the photo you want to use into a tiling texture yourself before trying to fill an area with it.
With a little effort, you can create your textures directly from scratch in PSP by starting with a solid color, then adding noise and filtering to get the effect you want, then making that into a tiling texture. In the above example, I believe the whole turn was drawn from scratch in PSP.
Depending on what kind of road you pick, getting the straight sections to line up right with turns can be tricky, so be prepared to redo the pasting into Traxx a few times until you start getting the feel of how it is going to come out.
just that i ain't good with graphics 