I recently bought Black Ops 1 on Steam, does anyone here still play it? There's a decent population in the multiplayer but it seems like there's not as many people playing zombies.
There are going to be custom maps for it soon, and although BO3 are getting tools I think BO1 maps are going to be great too since the actual basics are so similar compared to BO3. I'd give it a little bit of time and if people make BO1 maps once tools are public, there might be some more people playing.
I'd imagine some of the cracked multiplayer services might have some activity though, but with customs coming out soon I'd expect at least some of them to buy the game. Since the DLC content was not included in the BO1 mod tools, any content from the DLCs will have to be compiled by mappers, and in a nutshell means that when custom maps come to bo1, they will not require any DLC and that has a lot of potential for those unwilling to pay the 60$ for DLC to switch over to the official services.