Some of the best mods for Oblivion have been those which changed the textures. Although Oblivion was demanding at the time it came out, the rapid pace of PC hardware quickly made it easy for more computers to run. High-resolution texture packs helped ensure that players with cutting-edge hardware could push their gaming computers to the edge.
Now the same is becoming true for Fallout 3. This is hardly surprising, considering that Fallout 3 is actually not a graphically demanding game. It was built, after all, to be played on consoles as well as the PC, and gaming consoles have far less graphical horsepower overall. If you've invested a few thousand dollars in an insane gaming rig and you want to push it to the max, then downloading this terrain pack is a must. While Fallout 3's textures typically have a resolution of 512 x 512, this pack adds the option of resolutions at 1024 x 1024 or 2048 x 2048, dramatically improving the game's visuals.
You will need some serious horsepower for this, however. If you're not running the game's visuals at max already, then you may not be able to use this mod very well.