I just wanted to share an issue I was having that might save someone in the future a headache. I was trying to change one of the pictures in my dashboard, so I went to Appserver>Static>Images Folder and swapped out the pictures.
I then packaged up the app, using Splunk's built in packaging tool. I went to my test environment and uploaded the new app(with the new picture) and to my surprise the old one was still there. I must have spent hours double checking my code, and repackaging the app to make sure I wasn't at fault. Turns out all you need to do is clear your cache.
In conclusion, if your new images aren't loading on the webpage and you've tried refreshing the CSS via bump MySplunkInstance:8000/en-US/_bump. Try Clearing out your cache, it should do the trick.