Looking for a .gif for Category bands Background

[Limerick]

Hello all,

I've seen somewhere, but I unfortunately don't remember, a forum which had a background for Category bands made with a kind of "pointed" blue. It was a serie of dark blue points.

I wish to find it because this was the best way to make differences between categories in the default style even if they are separated.

Does anybody could help me to find it again?

In fact, as I can see, this is not simple.
Because i just want to change the top of the Category band, where its name is displayed, but the not the place where forums (or subforums are displayed).