The value of old art prints depends primarily on who the artist is, rather than the publisher. Some artists are very popular, with a large collector following.
And, some old prints are more rare than others. Some are more sought after than others, even if they're by the same artist.
There are many reproductions of the work of Bessie Pease Gutmann. It's very easy to find reproductions, but original old prints are hard to find. And the original paintings or drawings that were done by the hand of Bessie herself are extremely rare.
The condition of the art print is important as well. If the old paper is brittle and has turned tan, then the print will not be worth as much as a similar print in fresh condition.
Postcards are collectible in their own right. There are people who only collect postcards, so even though postcards are small and the art quality is not as good: they might sell for more than an old print.
All these factors will help determine Value. If you're just getting started, search online for the Artist first, taking these things into consideration.