i've noticed recently a few comps being posted with HUGE pictures.
There is a very simple way to make them smaller
[img width=500 height=300]
this is for pictures that are longer than they are deep
[img width=300 height=500]
this is for pictures that are deeper than they are wide
[img width=500 height=500]
this is for square pictures
you may need to muck around a little with the sizes if the image has writing in it for instance you may need 1000 width and 600 height.
after this code simply enter the url of the image as normal then