The Splunk documentation about customizing your app makes it clear that, in order to display custom images in your application, the images should be named in a specific way. From the section titled Add app icon images:
Icon paths are case sensitive. Example: static/appIcon.png, and not static/AppIcon.png. Refer to the table below for the case configuration of which images for app icons that Splunkbase supports.
If you want to add higher resolution images to your app folder, you should append a _2x at the end of the file name, e.g. appIcon_2x.png, to be used with high resolution displays.
This is all good, but what the documentation doesn’t clarify is that if you are on a high resolution display and you fail to add a 2x app icon, Splunk won’t automatically fallback to the lower resolution image. It just won’t display anything. This holds for every type of image, including app logos.
I was initially testing with a normal resolution version of an image but no matter what I did, I couldn’t see it in the launcher app.
So, if you are using a high resolution display (like a MacBook retina screen), make sure to add both versions of the app icon or you won’t see any image until you move to a lower resolution screen.