Can you help me? I want to make skins with vinyls/tribals on them but I can't make them myself... Skins with just logos are boring...

Use the path tool, it should make things easier for you.
Make four points on the skin about where you want the line(or 3 points), but don't position them perfectly just yet, as you will move them around.
Between the dots, you should have lines. If you click the dot and drag it, you will move the dot(edge), but if you click the line, it should start bending.
When you're happy with the look of it, click on "Path to Selection" button in the toolbox, which will then select your path and you can fill it with color.
It takes time and practice tho.
If you don't want to do it you can search for some vinils on google, like this:
http://images.google.com/image ... +vinyl+vector&spell=1

And open it as layer on your skin.
To remove the white stuff from the vinyl(if it's not transparent) select all the white stuff and right click on the layer in layer window and click "Add alpha channel", once done, just press delete and white stuff should disappear and you should see the rest of your skin behind your new vinyl. Just rotate/position/resize it to fit your skin.

Thanks for the help mate, I'll see what I can manage.

yep, path tool is quite nice, here are a few what i've done with GIMP







It's quite easy to create decent looking skins with gimp, when you find out how to use the path tool properly, then it is easy