According to Yahoo, 80% of the end-user response time is in the front-end rather than code generation. For Athleon, a large part of this is loading up static images which can occasionally be quite large (~100k). If you believe that your users' perception of speed is more important than actual speed, here's something that can help:
This loading icon generator creates a custom "loading" GIF from templates and a color picker.
Here's the one I created for Athleon: