Welll
You have to have a white/transparent image 19hx350w and make stripes using a pencil/thinnest paintbrush.
Then, save that as PNG and name it stripes or lines or whatever, and open it up, make the inbetween transparent, and make a layer. Push the new layer below the stripes, and then colour however you want, gradient or whatever. Then make a new layer and add text by googling Visitor TTF2, and going into the dafonts link that comes up. Enter whatever text you want into the tester bar, print the screen, make a new image, and make everything other than the text transparent. Use the bigger example. Then add it to your userbar. Afterwards, make some more layers, get some pokemon sprites, and add them in, each with a seperate layer.
Obviously you can experiment, and try out lots of other effects, but that's pretty much how to do it! :D
If you're like "HOW LONG WILL THIS TAKE?!?!" I'll make one for you xD