If you want a “circle” or a “star”, you can draw one in your PowerPoint presentation using the builtin shapes. If the shape you want isn’t there, you can combine several shapes or cut one out of the other.
In the following example, I demonstrate how to draw a “cloud” from ovals.
First I insert many ovals and place them in the following layout.
Next, I select all ovals, switch to the Drawing Tools / Format ribbon, and select Merge Shapes. In this example, I use union.