Gaiaonline profile background?

i have this pic, and i put it on photobucket so i could put it as my gaia background. when i did that, it turned out too small, and it tiled. i want to know if there's any way to make it bigger, cuz its already the biggest you can get it on photobucket, aand i want to know if i can make it "hover", like stay in place while you're scrolling down.