I bring home snow. Just small samples, mind you.
I keep them -- generally no more than a few ounces -- in baggies with notes on the date, area, conditions etc. The wife complained at first that there was no room left in the freezer so I bought a new one i.e. freezer, just for the snow samples.
I used to bring back a sample for every day I skied but that started to get weird so now I just bring back one sample, unless it's from a trip where I visited a number of areas, like in the Tahoe area -- now then I had quite a few because we hit a new place every day.
The only problem I have found is getting the snow back home after a flying trip, so I bought a portable cold box...I stuff it with dry ice etc etc. It's OK for most trips but coming back from New Zealand pressed its capabilities; and they sure did give me some strange looks at US Customs. (But when I tell them it's just a hobby they nod understandingly.)
Recently, I have been thinking of collecting simpler...like the patches you mention.... I am concerned about what would happen in a blackout. For a short outage we are covered; I bought a little back-up Honda generator to keep the freezer going. But what happens if we are out of juice for a week and I can't get gas? It's troubling. And sometimes a hobby just becomes so draining that you have to stop. So be careful with those patches. And the stickers might get really dicey.