I’d like to suggest adding an option to use these rainbow logos as actual in-game entities, not just in the menu. It would be fun to place them in the world as decorations.

It does actually do that but these entities are only placable in editor and are under the unsorted tab.
Since the mod replaces the texture of the original entity with the one you have selected in the mod settings you can only place your selected one.
I will look into how to make it possible but I haven't done any recipes or research with modding before so it might take some time.
It will probably stay at only one of the logos being a placabale entity (the one you selected at the menu) because it will add the 3 different sizes factorio has; 11 tiles, 16 tiles and 22 tiles wide and if I included all the possibilities it would result in way too many items in the build menu.

I'll try my best to implement this but can't promise anything since I haven't done it before.

Okay I have managed to make it work and updated the mod to version 2.0.0 which now has craftable and placable logos.

Thank you for the suggestion, this was really fun to explore and learn! Hope you enjoy placing the logos around the factory as decoration!

Thanks~