Working on using large map files for a background…
Creating large mesh-plane(s) of various dimensions, so that the images for the texture do not have to be stretched, but almost everytime I go over 1000-2000 in DimX - DimY it disappears from the screen. I assume they may be too large as a few times they have appeared they are way over the edge of the square grid pattern in the middle of the screen. I am working on a Dell 7000 desktop, with a Nvidia GF7950x2, on a 30" monitor. I have compressed my texture images already more than I wanted to, any further they would be too fuzzy to be worthwhile. If possible I would prefer them in the native 4000x8000 pixel range, but that never works.
I ran into a similar problem trying to use 3D Max, seems to be a limit on the texture and model size.
I’m not quite sure what you mean.
If you mean that the plane disappears from view when it gets to big, this is due to the View Clipping, which can be changed in View>View Properties>View Camera in the ClipEnd number button.
Some more info would be helpful. 
BTW, if you want a plane to automatically scale to the size of an image, apply the image as a texture and press Alt V.