Any graphics program will do. Based on the question you asked, its safe to assume that you are a novice to graphic designing. So, the best programs to use for novices are:
The Gimp (Freeware)
Photo Pos Pro (30-day free trial)
An intermediate grapics program for when you get more comfortable with the basics of photo manipupation:
Paint Shop Pro 10 (30-day free trial)
Then there's the benchmark for all ADVANCED 2-D graphic manipulations:
Adobe's Photoshop CS2
In order to create stunning images with Photoshop, you will need alot of patience, practice, practice, and more practice! It's NOT a program that's easy to learn and is HIGHLY recommended for intermediate to advance users ONLY! Plus, Photoshop comes with a hefty $600 price tag because it does MUCH MUCH MORE than make sigs. Its a professional commerically used program that is designed to be both complex and detail intensive.
A good portal for tutorials on many different programs:
http://www.pixel2life.com/
If you feel adventurous, check out
Deviantart.com and check out some of the different works of art of various programs and their users. The above link is their resource page. You can further define the different aspects of programs by changing the sub-catagory pulldown button at the top center of the page.
Linear Mode
