Here are a few suggestions. A local hobby store might appreciate them to put on display. Most stores, at least on this side of the pond, have some kind of case to display finished models, to show their customers what can be done with the kits they sell.
You might also look for veterans organizations, to see if they would like to display them. Or local museums.
I used to work at a desk and I had some on display in my cubicle.
You can always try to sell them on e-bay.
If worse comes to worse you can pack them away once they have been on your selves for awhile, to make room for recent additions.
My SWMBO is less than enthusiastic about me getting new kits, so I feel your pain. She is fairly complementary when I finish a kit though. Guess which reaction I get the most of, disgust when I get a new kit, or compliments when I finish one?