Looks like that was done with a combination of modded race and console commands. They took screenshots, saved, exited out, increased size of race in construction kit, re-loaded the game then continued repeating that. You can't get that big only by using the console.
Console commands (hit ` key to bring up console)
Select your character then type:
Setscale 1 (normal size)
Setscale 0.5 (half size)
Setscale 2 (double size)
0.5 and 2 are the limits. This restriction is removed in Fallout 3.
With the console and these spells you can either become twice as tall as normal or half the size. If you want to go any bigger you need to download the Oblivion Construction Kit and create a new class (like Giant) and set the initial size to a number larger than 1.
If you set it to 2, for example, Your normal size is double-height. You could shrink yourself to half size and interact with the world normally if needed. But if you then enlarge yourself you're quadruple normal size.
Here's a quick link to a mod which gives you some size-changing spells.
http://www.tesnexus.com/downloads/file.php?id=21696
There are some mods which will give you a slow growth effect as well, I can't find em at the moment.
Personally I use this mod:
http://www.tesnexus.com/downloads/file.php?id=33044 to create a good looking character. Took it into the construction kit, duplicated the race, gave it Nord stats instead of Imperial and changed the default height to just a bit taller than Nord males. Nice amazonian size imho.
If you use setscale to make yourself taller than normal you revert to normal-height when talking to NPCs, suddenly being short again gets distracting. By setting your base height to being tall in the first place you avoid that.
...and if you're playing on a console forget everything I said cuz you're out of luck.
I just recently reinstalled Oblivion myself and am having fun modding the heck out of it. This is what my current character looks like:
http://www.tesnexus.com/downloads/im...1281682716.jpg HGEC ftw.