Is there a program that will let me open up installers like those for Chrome and Palemoon browsers, and replace the generic type installer icons with icons that are more visually specific to those browsers, and then repack them back into install files?
I think you may need two applications for that. The first is a resource editor such as Resource Hacker. You can extract icons contained in dll files. As for the second ... it depends on the type of packaging. I think Google Chrome is distribuited into two types. 7zip and MSI. Palemoon seems to be a self-extracting exe file. There are several tools to prepare the packaging. Good luck!