Coming from the perspective of recognisability, I think most of the old icons are better. For many of the new ones, there is just too little contrast between the background and the actual item, obscuring the item's shape. Also, they feel dim and dark, and have a lot of unnecessary busyness in them. I do like the less prominent lines around the icons, but overall I feel like the new icon set will be harder to use, and I'll end up just memorising items by position rather than icon for easier shopping.

Good:
Blade of Alacrity, Ogre Axe
Ultimate Orb
TP Scroll
Bad:
Almost every other icon. Seriously, the staff of Dagon is barely visible! Arcane Boots doesn't look clearly like a boot at all! Force Staff looks like a green blur (not quite, but consider eg. people watching a stream in less than HD quality. That's all they'll see!) Heart of Tarrasque looks like a meteor or something!

I would really prefer if you stuck to a simpler, cleaner style, and didn't just add detail for the hell of it. Don't get me wrong, these are some great illustrations, I just don't think they are suitable for their intended purpose (easy and quick recognisability, while fitting into the overall art direction of the game.)