No problem, good luck with your build. I'm not familiar with the Intellivision Flashback image, but if the theme will accommodate them and you want to go next level, you may want to consider adding video previews and marquees. I've been working on my RetroPie image on and off for the last few year and that was the best addition I've ever made (other than the games themselves). Basically you scroll to a game, a marquee for the game appears at the top next to the system logo, the box art appears for a few seconds, and then a video preview replaces the box art. You can even set the screensaver to play random video previews. It's pretty sweet. This is the general idea, although they're using a different theme (I'm using a modified version of the stock Carbon theme).
Most of my other systems are finished and I plan to start working on Intellivision next weekend. I'm not thrilled with the quality of the publicly available video previews for Intellivision, so I'm going to record new 30 second previews of most of the original 125 plus several dozen homebrews using jzIntv's built-in recording functionality. If you're interested I'll see if I can find a way to upload a zip file of finished videos and marquees. Videos will be 480 pixels high and marquees are all sized to fit in a 400w x 110h space. Adding them to a theme is not terribly difficult and I can walk you through the process. You will need an image that's running Emulationstation 2.7.6 or higher.
Also, if you lost track of your custom palette settings, unbeknownst to you they were immortalized in the RetroPie docs under the "Using Custom Palettes" section at the link in my original post!