Semi-constructive criticism in order of appearance:
Medium electric pole:
-The lighting on the top is a bit much and the viewing angle makes the proportion look all weird. The top looks way bigger than it should be compared to the in game entity. The rest of the power poles also suffer from this.
Roboport:
-Very fat looking, we only get to see the top half of the roboport in the icon. It misses the iconic spinning radar thingy and lots of other details.
Beacon:
-Anal probe? Suction device? Futuristic miner? Tesla turret? What even is the new beacon design?
Nuclear reactor:
-This one is the worst, it looks way too cute and cartoony for a NUCLEAR reactor. Right now it looks more like some sort of weird hat without a brim or an odd toy. Its doesnt even remotely resemble the in game nuclear reactor
Low density structure:
-I can't put my finger on it, but the wavy structure combined with the color and holes feels really disturbing. The greenish tint especially. (r/trypophobia ?)
Flamethrower turret:
-A very odd abstraction from the real turret with wanky proportions. The in game entity is long but not very high, meanwhile the icon is very cramped and stacked. The lighting is very odd and gives it a very cartoony look
Accumulator:
-This one is not that bad but the electric sparks are very prominent in the design, but at the same time don't really feel sparky, and just connect the electrodes in a line
Pipes:
-The cap and brim are way too thick which makes the icon look very odd on belts compared to the original which was rotated 90 degrees and less bulky.
The engine:
-The engine icon itself looks cool, no problem with that, but the moment you put a few of them on belts it looks like a line of ominous toasters with exhaust pipes. Since Engines are intermediate products they will be on belts a lot of the time.
The style of the new icons overall shifted more towards a cartoony/artistic representation (cough cough combinators) of the in game entities this update. Instead of just a smaller version of the original. For some items this makes it hard to guess what the actual item will look like based on the icon, for example the roboport and the Nuclear reactor.
The switch from a high contrast light background in the crafting GUI to a much darker grey makes it even harder to quickly find items, because you can't really trust their icons silhouettes anymore because most of them don't match their in game counterparts.