I've figured out how to change the background to a Gif-file, but I cant figure out how to make it stick so I don't get an repeating picture when I'm scrolling down.

What i want is to make a background with one symbol on each side of the site (have made the with 70% so there is 15% spare room on wach side). I want these symbols to stick at the same place when im scrolling down.

Is this possible.

Yes, use

background: url(/path/to/image.gif) no-repeat fixed center left;