Seems to be a problem when I try to edit .ini values... The main problem is that the line is simply not there.

For example, from a GameSpot guide: http://www.gamespot.com/features/6148788/p-2.html:

iPreloadSizeLimit
bBackgroundLoadLipFiles
bLoadBackgroundFaceGen
bBackgroundCellLoads
bLoadHelmetsInBackground
iBackgroundLoadLoading
bBackgroundPathing

and many others are missing from my ini...

Any tips on what to do? Is it just safe to just add the lines to my config without hurting anything?

First off make sure you are editing the correct .ini file !! the Oblivion_default.ini is the one the actual oblivion.ini is created from on first launch and should never be changed -- so if that is the one you are editing that would be why those lines are missing. The correct one to edit is located in your USERNAME\My Documents\MY Games\Oblivion\ folder not the games installation folder.

It's the correct one.

I've looked around the web and some people say that the lines just appear miraculously.

If it's not too big of a problem, does anyone have a fully optimized .ini file I could refer to? I hope it's not too big of a problem for what I'm asking...