I checked the size of files and they seem to be all right, 32 x 32, and I believe the problem must be somewhere else, like in the addon itself. I wonder if I should ask about it in a different section.
The addon uses stanbdard ACE-3 libraries including LibStab, HereBeDragon, and CallbackHandler. I am trying to alter something that uses a different way to me of pointing to icons to render. I don't even know what I should ask about. This addon uses a really convoluted way to get texture via function call of function call of function call which eventually calls GetAtlasInfo() with "atlas" as an input and returns a texture which is then trimmed.
Originally, the addon uses a few icons that author refers as "PortalRed", "worldquest-icon-tailoring", and "Garr_TreasureIcon". This does not looks like an internal icon names such as "INV_Jewelcrafting_80_Gem02_Blue" which refers to a blue gem. There are not extra tga/bpl files in an addon folder, either. I thought they would be in a HandyNotes (core) folder but there are not! I am completely lost here. It must miss something obvious, yet I don't know what it is!
EDIT.
I found it. The source of icons used in this addon is from `AtlasInfo.lua` (
link to FrameXML). I finally managed to get textures from my own file and render them on map. That was quite an adventure
