Jesse recently uploaded a bunch of generic textures that people on LiveJournal can use.
Look how pretty my journal looks now!
It's not super simple to use yet, but it will be... we're gonna make an S2 customization widget (from the /customize/ area) to let you pick a texture (along with our existing DHTML color picker) and see the texture change in realtime and apply it to your background, etc.
This dumb hack never ceases to amuse me.