Depends on which you want to target your audience to -- whether it br a low-end system, or a high-end system. And, that depends on whether the requirements will be higher or lower.

Also, most of the games like in Neverwinter Nights have a detail slider to adjust the resolution. Here's my thoughts on how this works:

Setting the detail slider to low will:

• set the resolution of a textures to a low resolution such as 64x64 or 128x128,
  
• make the textures look less detailed,
  
• take up less memory,
  [*[and will fit to a minimum of 4MB of video memory or more.
  

Setting the detail slider to medium will

• set the resolution of a textures to a medium resolution such between 128x128 to 256x256,
  
• make the textures look more detailed than setting the detail slider to low,
  
• take up more memory than having the detail slider set to low,
  [*[and will fit to a minimum of 8MB of video memory or more.
  

Setting the texture detail slider to medium will

• set the resolution of a textures to a high resolution such between 256x256 to 512x512,
  
• make the textures look a lot more detailed than setting the detail slider to low,
  
• take up more memory than having the detail slider set to low,
  [*[and will fit to a minimum of 16MB of video memory or more.
  

Generally, when you release a game, you should have a gamer set their texture detail slider to their liking -- whether a gamer has a low-end system or a high-end system. And in that case, you will need to setup a options panel with the slider before running a game starting script.

Anyway, I don't know how this will work as you might have to have seperate wmb files on whether a detail slider has been set to...probably something like:

lowdetaillevel1.wmb
lowdetaillevel1.wad
lowdetaillevel2.wmb
lowdetaillevel2.wad
highdetaillevel1.wmb
highdetaillevel1.wad
highdetaillevel2.wmb
highdetaillevel2.wad

I think this should help you out but this is just my thoughts about how are you going to target audience...