If my calculations are correct and the reported size of the image map is right, that's a a 6.5GB image when uncompressed.
Frankly I'm not surprised you're having problems in that case. Even if you had 8GB of RAM TG2 isn't yet capable of taking advantage of it since it's not 64 bit.
TG2 definitely needs better handling of image maps, including functionality to only load the part of an image that is being used in the actual render. Still I think it is a lot to ask to use an image map of that size. Some way to support mip mapping (multiple resolution versions of an image for different distances) might help. I'm quite sure we'll be improving handling of large textures in general, but I don't know the details of how exactly that will be dealt with.
As for rendering at larger sizes, this is definitely an area that has not yet received a great deal of development attention. Rendering at print sizes is not something I would recommend in the Technology Preview both because of the unoptimized state of the application and because of certain known memory-related issues with rendering at larger sizes. It's certainly possible to get it to work, but you are likely to experience frustration in the process, including crashes, lost renders, etc.
Keep in mind you're dealing with a Technology Preview here. I know it seems odd sometimes that many things work so well and yet others can be completely broken. It can lull you into a false sense of the application's maturity and you expect it to do things that perhaps are unreasonable. This is simply the nature of the development process. Many things will improve and much more will be possible by the time the final release is made later this year.
- Oshyan