Easiest way to tell a stamped receiver from a milled one (on a picture) is presence of rivets on the stamted ones. You will see (usually) 3 rounded rivet heads on the front and 2 in the rear. Most milled receivers have lightening cuts on the sides above the magazine well. These are not present on all machinned receivers though.
There is no way to tell an AKM receiver from an AK-74 one by just looking at the picture. The only differences that i know of are:
-slightly narrower magazine well on the 74
-some very minor internal differences
-stampings on the receiver, obviously
Most AK-47's had milled receivers, early ones (Russian Type-1) were stamped, but you will probably never see one. Most AKM's and AK-74's had stamped receivers. However both exist with milled receivers also.