I am using Yahoo Mail.Hello,
Are you using Yahoo Classic or the new Yahoo Mail ?
What are the extensions of the images? (jpg, gif, bmp, etc)
Have you tried reducing the size of one of the large pictures (3MB) before attaching?
I've started forwarding around a set of different size pictures with different extensions trying to find if there are limits for the size/type that Yahoo will display.
Also, since you mentioned forwarding, is this only when forwarding pictures or when attaching them to a new email too?