I maxed out with 7 (+ a regular follower). After the ones you see below, further quest followers seem to lose track of the group far too often and Barbas is too annoying not to be shot in the face before taking the picture.

Followers on-screen

Esbern, Delphine, Mercer Frey, Maurice Jondrelle, Thonnir, Enmon, Dark Brotherhood Initiate, Marcurio.


Eola, Avulstein Gray-Mane, Thorald Grey-Mane, Geirlund, Vidrald.

More followers?

You can add more information on Multiple followers or use the comments section below.