I'm running an Old School Essentials campaign at my friend's board game bar, The Pint and Pawn in Biddeford, ME.
For this campaign, I'm painting every model that the players will fight or interact with. We play once a month, so that gives me time to order the models needed for the game and paint them. I'm also home-brewing everything, so I can just make sure they are only going to encounter creatures that I already have models for!
The models I'm using are from Otherworld Miniatures, and the quality on them is frankly outstanding. They have literally any models you'd want for an old school D&D campaign, and they are very high quality sculpts.
I've been painting models since I was 12, and these are some of the highest quality fantasy sculpts I've ever seen. Games Workshop has higher quality sculpts, but they are out of scale, have giant weapons, etc.
On top of the sculpt quality, the models are understated in a way that is very hard to find now. Most models designed for D&D today look like a World of Warcraft character (giant armor, huge weapons, etc.) These models look like they could have been historical models (they have accurate proportions, the female models have realistic armor, etc.) I'm hoping to buy and paint a whole set for old school D&D as an ongoing project.