Skip your different collection themes & topics such as this one & the "Zoo" have inspired me to find my own "theme" for collecting. I have contemplated what "theme" or "topic" I should go with for months now but couldn't find any. For one, it's a question of availability. Two, it's a question of price. Three it's a question of interest.
The other day it finally came to me when I bought a Colonial advertising knife. (It's in the mail.) My collection theme (with a very wide & general focus) will be advertising knives that have to do with "Transportation". Garages, Car Parts, Gasoline, Shell, BP, Car brands, Car dealers, ect. ect. but also not to exclude other forms of Transportation such as Planes, Trains, Boats ect.
There seem to be enough knives over here within this "theme" to keep me happy without killing me financially. Now I just need a place to post them in the future to keep them all together in one place.
Edit: Maybe I'll drop the "theme" and just collect advertising knives in general. I'm not sure yet.