RTF is a global modification that replaces all towns in the game.

I don't like the new icons because they lack a consistent style, although their informativeness has definitely improved.

Yeah, the style changed as the work progressed – initially, I wanted to use only icons from Heroes 5 (the town hall, shipyard, and school of magic were from there), but I abandoned that idea because of the low resolution of some of the icons, so I started taking them from the internet (tavern, market, guild of mages, forge). Then I ran into a problem – I couldn't find an icon for the gate on a black background, so a third style appeared, and then I got to the units and decided to give them a black border like the other buildings (but it needs to be changed too, because it looks a bit out of place).

Added 11 minutes later

I think this hurts the authenticity, but – I noticed the small hint icons in the corner. There are hearts, plus signs, and so on.
Perhaps this is the direction to explore, so that the icons depict buildings, but also graphically show what they do. Like a beer mug, crystals, an IV symbol in a mug for the fourth-tier creatures, etc.

That's a good idea! But then you could make two versions – with small hints and a complete replacement of the icons (my sister's eyesight is bad, she won't see the small hints).