A good workmanlike shadow is being used on some images that might be improved with a little tweaking. The sample below, again a very simple approach, illustrates the point.The left glass has a shadow applied, created from the shape of the glass on a separate layer, blurred and distorted to make it appropriate to the image. While its a decent shadow and works to sit the glass down it could be improved.The right glass has the same shadow with some photographic principles applied. A shadow is usually darker and sharper edged at the base of the object casting it and becomes lighter and softer edged as it recedes away.Translucent and colored objects also cast a bit of their color into the shadow, particularly at the base. A thick-based glass object may cast a highlight into it as well.On separate layers, I added, using the airbrush at 10% opacity, a darker tone cast at the shadow base and a hint of the object color to most of the shadow. A dot of light highlight smudged as a reflection at the base finished it off.Hope this provides some help. :)