Get frame animator 2.7 (I'd link it but on phone atm) Automate the frm you want to modify and edit the picture it extracts. Add new frame (edited picture) to empty frm and save with the same name of the one you modified (so if I want to change BAG.FRM, I'll name the new one BAG.FRM) and IN YOUR FONLINE CLIENT, make folders such as data/art/ and last depends where that FRM is located. Like adding edited weapons would be data/art/inven.
Hope you understand :V
As for modifying resources and lockers, there are mods already for that, just look for them here in tools section.