Is there a way to tell Blender NOT to load certain images during render? So I have this problem, renders take too long because its loading unnecesary images.

I'm working on an animation and I'm using very large Images with all the character frames.

And I want to somehow tell Blender to skip loading certain images during render, until it becomes necessary for the shots 

here's a more practical example of what I mean
(understand that I have like >50 materials in my project so manually adding and animating mix node like I did in example would be really tricky as well)
This can be achieved by enabling "Use Camera Cull" in the Simplify settings in the scene tab, though it will remove entire objects that are not in the camera's view instead of just textures and will affect reflections/shadows as a result.



An alternative solution to your problem is to enable "Persistent Images". Blender will keep these large textures in memory instead of reloading them on every frame, thus reducing your render time on subsequent frames without altering the final image (shadows/reflections) in any way.