Lately, I work a lot with Sigil, Calibre, and kindlegen. I was fed up with the generic icons set by Calibre for the ePUB, MOBI, and AZW3 formats. They are great but they are all the same for the three different formats.
Surprisingly, there aren’t many, if any, free icons available for what I had in mind. Nor, for that matter, much of a consistency between their various takes.
So I pieced together something on the fly. The initial concept isn’t mine. The general look comes from another person’s version for the MOBI format. Colors are extrapolated from what the Internet seems to think they should be.
No credit required. You are free to use all three as long as it’s for personal use only. However, if you intend to use these icons for a publicly available or commercial project, make sure to triple check if the original icon/icons on which I’ve approximated mine aren’t, in fact, heavily copyrighted. If you think the coast is clear, do whatever you like with the icons. It’s not my intention to be a dick. Just a fair warning.
In some cases, changing the icons in Windows 10 might be tricky. Do the following only if you are stuck. Basically, if you have problems assigning an icon only for one of those formats, your best bet is to detach this format from the application that opens it, and also, most likely, deleteing that format from Windows Registry and recreating it manually.
The basic schema in Windows Registry for ePUB would be something like this (all the action is in HKEY_CLASSES_ROOT):
Make sure you have detached/deleted beforehand all previous traces of ePUB, MOBI, or AZW3 file type definitions and program associations in your system. You might also find useful File Types Manager and/or Default Programs Editor for a better look of the situation.
Restart, if needed, and then just choose a default program to open the specific file type of your choice as you would normally do. It’s a chore, but totally doable.
PNG and ICO format: Download ePUB, MOBI, and AZW3 file type icons