Avoid using an excessive number of images
Impact area
Performance
Severity
Medium
Affected element
Apex Page
Rule ID
SF-0131
Impact
Images are frequently the largest components of a Web page and thus significantly affect performance.
Remediation
Use fewer images and smaller background textures, and use CSS instead of images whenever possible.
Time to fix
30 min
References
See the Salesforce documentation article: Visualforce Performance: Best Practices > Optimizing Image Usage.