I teach United States History II to 11th graders. I always kick off a unit with an activator that is usually a drawing or political cartoon. I find having the drawing projected as the students enter the room helps to get the class rolling. I will have them answer questions like the ones you see on this worksheet in their notebook while I take attendance and/or check homework by row. By the time I've finished, we are ready to discuss.
I like to ask what the students see in the picture. If there are no volunteers, I call out names on an index card. Once students start describing the picture, "A lady is cutting the Native American's hair." I will then probe and ask why? And then begin to discuss assimilation. It would be a good idea to have assimilation defined somewhere on the board.
Other ideas would be a turn and talk to your partner about the drawing and then have a report out after five minutes. I like to set a timer. Other ways to use this would be to make copies and hand them out as the students are walking in while also having the drawing projected on the board. They can begin working right away.