Though it's been over stated you'd have to have a very old and decrepit computer for some simple gif/jpg snowflake images to cause a major dent in your CPU performance.

If it's causing a major dent I think it's time to buy a new computer. You can get a well priced one from any major retailer.

If that is not a prossiblity then you could download a computer performance increaser program. The two I can think of are TuneUpUtilities and SystemMechanic