random book texture problem

i am trying to make a libary, and i have textures with the same dimentions, so i wanted to make a random texture material, but the setup only chose the first and the last, and nothing in between, this is the simplified version:

so i made 4 colours, with a mix node with a factor of object info: random, and it only choose blue and white only when i gave 4 different colours, what is the problem?

this is the actual node set up, i only tested it after i made so far, basically, texture with uv, into diffuse node, to the same thing as above

Try this

thankyou, but how would you get around of doing mare textures?

More? Add another group node and make it unique - click on where it says 2. Assign more textures.

In fact there might be another solution involving selection of part of the big texture or using python script.