What's been said goes double for non-baseball stuff. There is a wide variance in prices that can be exploited to get some really great stuff. Of course, everyone has their own likes and dislikes. My tastes run towards team issues and athlete promotional issues, which have a card 'feel' to them.
I also like Hollywood issues, especially when they are linked to a known photographer or were studio pieces, lobby cards, etc.:
For the subjects I actively collect, I tend to grab any interesting image, regardless of 'iconic' status. I also tend to pick up pieces that come from studios with studio embossing, signatures, etc.:
A double-weight wet signed portrait of Georges Carpentier from the Geisler-Andrews studio, a business that operated from 1917-1921.
Hall of Famer Fred Welsh in a 1911 photo by George Grantham Bain
10.5" x 13" portrait of Jim Jeffries embossed with the logo of the Dana Studio in San Francisco.
