ok, if you want it to make yourself, get a program like photoshop, paint.nt or GIMP.
(photoshop is the best one) you can get a 30 day trial on the adobe site.
or... you can go to the GFX section on the bottom of the forum and you can request a signatre.
Hmmm I'm not sure about lunapic because I've never used it but if you want a good program try GIMP because it's free. If you find making them is not your thing, you can buy/request one at the GFX part of the site. I have an auction, but they're are old sucky ones so you probably wont want one lol.