The Crop tool allows you to Cut off the unwanted edges of your pictures. After that, see how to resize your image bigger or smaller with image scaling.
See how to put layers in a straight line on your canvas. If you have small layer shapes like circles, you will need to make sure the layer border is reduced to the edges of the shapes (using autocrop).
Encapsulation allows you to group object layers. You can then apply gradients and other effects to them.
Make a square shape with patterned edges.
Paint on your canvas using a series of images as your brush. Also called image pipes or image stamping.