theres a couple mods there let you go to new zones which have chests for you to store things in. theres also the thing with the toolset where you change the amount of space you have. check the dragonagenexus website for them
You can change your inventory capacity in the toolset, it's not difficult, takes less than 30 seconds. I'd be glad to give the instructions if you'd like to know how. I do it at the first save of every game, the capacity stays with your character even in Awakening and Golums.
Best DA:O Daggers ever: http://www.gamefaqs.com/pc/920668-dragon-age-origins/images/screen-86
If you get really big, as you can with some of the bigger mods, you'll exceed the amount of memory that Dragon Age is supposed to occupy (page memory? Can't think of the term atm. Heap size?) and you'll get some weird performance. If it is heap size, you can change that fairly easily.
300 for me is more than adequate, I never go beyond items even with all my armour/weapon/etc mods that dump everything in right away. I've done 500, but that's just ridiculous, imo.
In the toolset, open the .das file (I only do this in the first save of the game, have no idea what happens later on especially after purchasing backpacks.) If done at the beginning, no backpacks will be sold by vendors, if ever there are backpacks to be had, do not purchase or inventory will revert, but that's never happened to me.
1. Open .das file (ex. Human noble origin would be CastleCousland.das)
2. Expand: SAVEGAME_PARTYLIST
3. Go to: SAVEGAME_MAX_ITEMS - Click on the 70, then overwrite it with whatever you want, I use 300 (70, of course, is the starting item amount in your inventory)
4. Then save the file: File>Save as>then save as the CastleCousland.das file, your old one will be backed up.
Takes seconds to do, instant results.
Best looking daggers in DA:O - http://www.gamefaqs.com/pc/920668-dragon-age-origins/images/screen-86
The easier thing is simply not to pick up all the garbage along the way, seeing as most loot is crap. If you don't have soldiers keep for extra storage, or if you just think it it should have been included from the outset get a mod like Misha the Hoarder who is party storage for your camp. If you do that and don't just "take all" every time you loot you'll fine 100 is more then adequate.
"Whenever I find myself on the side of the majority I feel I must be wrong" - Mark Twain