It seems from rapid tests that using in one of the containers in the houses of whichever of the two families welcome you in Riverwood (Alvor the smith's for Imperials, the woodcutters for Stormcloaks) may work fine.
These containers arent yours of course but there doesnt seem to be any respawning in them, you can use them without it being seen as stolen, and no NPCs have raided the [censored] out of my warchest yet despite waiting a week outside.
But thats FAR from conclusive evidence, just something you can gamble on.
The only things Im 100% confident in right now are the houses you buy in the various cities and dragon corpses. The latter are marked as plot, and will never vanish, and no NPC interacts with them. Theyre usable, but its of little consolation for those unwilling to immediately tackle the main quest and deal with random dragons.
The main reason why just selling everything doesnt work is of course thieving. Cant sell back thieved items and its good to have a place to stash my ill-gotten gains early on

By the way, for fellow thieves, do yourselves a favor and visit the lady who owns the riverwood inn at night. Orcish bow, elven dagger, three good gems, 3 regular healing potions 3 big healing potions, and a solid 7 points of pickpocket if you manage to get it all
