Yes, it's possible, but physically, in a paint program. Poser allows you to decide a max texture size when rendering, so if you have , say a 4049x4096 texture, you can tell Poser to reduce to 2048 when rendering, but it doesn't reduce phisically the image, it just creates a lower res virtual version in memory and only when rendering. Upon saving the scene, the real texture size is saved. But Vuedoesn't have this option, so you'll need to create lower res textures in a paint program, which is going to be quite tedious, since you'll have to retexture everything in Vue.