I've finished the game twice now but haven't really found things I'd find interesting to hang onto for housing decoration.
For example, in Fallout 3 I liked holding onto Is there anything like it in Vegas?

There is space suit.

Doh yeah now that you mention it... I actually picked it up but I guess I forget to
mention it because I actually needed it (for rad resistance) in this game.

garden gnomes of course...

If you get the formjulas to make em id expect nuka cola quartz and victory would be fine decorations..

Can you drop the rocket ships they glow nicely...

dinky the dinos of course..

duct tape.. lots of duct tape...

I find mut fruit looks cool specialy with some cactus fruit..

certain energy weapons realy look cool on a shelf.

plsma mines and emp mines and nades of both types realy look cool.

always lay a bunch of magazines on your coffee table.

I like the Dinky the Dinosaurs but they lost their charm when I was able to instantly buy a 1000 of em...

Grab all the glowing green absynth from the atomic wrangler.

I like to decorate my Lucky suite with unique weapons i don't use.

Something about entering your office and seing a Minigun on the coffee table that makes me all fuzzy inside.

Your characters name would not happen to be Tim Allen would it?

The one thing that is a must in my house is a copy of the Wasteland Survival Guide on the desk.

Food Sanitizer, Rocket, T-rex

i f ound an acoustic guitair, not sure if it is quest related.

Just a sidebar: how can you drop the damn rocketships? The only way I was able to get rid of them was to give them away to other people for specific purposes - for the full-sized rockets or to make nice to the Boomer kids. Otherwise they're stuck in my inventory forever (I'm on the 360). Guess I'll have to settle for glowing sodas.

Unfortunately, not until they patch it.

I am also kinda miss a butler robot....yes, even in Novac......