Time Machine doesn't always format your drive. You can use Migration Assistant with its backups, as well.
Disk images, by nature, wipe your drive and replace it with the data in the image. However, if this is the way you want to go, use Carbon Copy Cloner. It serves the imaging thing well.

---

Custom Hackintosh...AMD Athlon X2 5000+ (2.6 GHz) on GA-MA78GM-S2H...Linksys WMP300n Wireless...ALC889a sound...ATI HD 3650 PCIe...1 GB DDR2 RAM...320GB Western Digital SATA + 200GB Seagate IDE HDD...Rosewill DVD-RW IDE...Running Kalyway upgraded to 10.5.7...All Fully Functional