So what you're saying is you've run out of grey balls, lol
Easy enough in max 9...just go back into material editor/Utilities/Reset Material Editor slots. You won't lose materials already in scene; just get a new set of grey balls
The only problem with large texture sizes is could be laggy on some people's systems. To be honest, I've found with experience that unless have high-end system and staring at detail close-up (like in Type 9 cockpit) large textures don't make huge difference. Unless you're real close, little difference between 1024 and 2048 lcars, and I'd argue 512 ok. Any plain texture (carpet, wall) etc need be no larger than 128 or 256. Average lightmap is 256.
512 or higher best for areas where need a little more detail - wall or floor lightmaps with light/shadow detail, lcars
But go with you what you think best and if necessary release bridge with a cut-down medium folder as well.