Italy, Germany and Japan if we want to include the era where the UK was imperialistic. If don't want to include those then including the UK/France flags is unfitting.
Otherwise it's also missing the flags of China and Russia
There's a lot of newly found natural resources in southern and eastern Ukraine. It's funny how the same "imperialists" are always the butt of the joke while there's an actual, massive imperialist war of conquest happening right now. E: testing if editing federates this.
What I'm saying is the timing on these memes about past European imperialism make them look absurd with what's happening in Europe right now. All the countries listed in the meme are helping a country fight back an imperialist, expansionist warmongerer.