Sample of the BitMotion Rollover module. Choose your initial and rollover images. This one is setup to immediately show the rollover image, but to have a 1 second delay before switching back to the old image when the mouse leaves the graphic. Note that the ALT tag supports international character sets, so you're not limited to only using English.

Hold your mouse over the image for 2 seconds to see it change. When you move your mouse outside, it takes 2.5 seconds to change back. This one is just like the above, but with the images switched. It also has no border and doesn't provide a link or ALT tag. You control exactly how you want it to look and operate!