Every cause should have icon asociated with it - this would enable three awesome visual enhancements:
1. every build could have trigger badge
2. there could be custom column which shows last build trigger cause with icon
3. every build for prject could show cause 48px icon on its run page

Now ideas 1. and 2. are implemented using custom plugin Build Trigger Badge Plugin

Idea 3 will greatly improve visual identification of build:
a) if build was started by user Example1 there would be user profile icon.
b) if build was started by timer Example2 there wuld be 'clock' icon hourglass.svg

Provided icons should be in all common sizes in Jenkins (48, 32, 24, 16)

Related discussion https://groups.google.com/forum/#!msg/jenkinsci-dev/Qh4XkVbu6ug/22iCrmPQ8xEJ