Answer:
What I see in the Placard.
A Caucasian man washing his hands with soap which is surrounded by pictures of what was considered to be parts of civilization in those days. There is also a picture of a white man giving a black man soap.
Cause of New Imperialism ⇒ Moral obligation to help "uncivilized" people.
There was a prevailing view in the 19th century that the white man had the moral obligation to help the parts of the world that has not reached their level of civilization to reach it.
This picture shows that view because it believes that much like using soap to wash away dirt, the white man should help the "uncivilized" nations and races to wash away their perceived backwardness and become more clean and civilized like the whites.