As @realmadrid1809said, the icon IDs for those monster icons are unknown. If someone does find them, let me know what they are and I will update accordingly.
Thank you, @realmadrid1809, for taking the time to look into that problem. However I won't use your edited file to replace the main file, at least not yet.
I don't know exactly what you mean by "re-exporting" in this case. But whatever it is, it increased the size of every icon by a decent amount, causing your version of the mod to be over 7 times larger than the original. Until the bug is fixed or until I otherwise have a better understanding of the problem, I won't replace the main file. However I will link your modified mod to the main post for anyone who wants it.