Overall

If you are looking for an alternative source of diorama pieces here is one. PetSmart has a line of poly-resin aquarium pieces that range in size from a small wall to large columns and ruined monuments.
I purchased the small wall to get a good look at it side by side with a 1/35 scale figure and to get a feel for how it can be worked with. The variety is decent and flexible enough to work many of this line into a number of different dioramas.
The detail is good and the overall appearance works well. It is not a cartoonish type of product at all. Add a bit of paint, a wash, some pastels and these products will fit right in.

Scale

As with any 'non-modeling' product scale and appearance are one of the key considerations. As you can see by the image these will work. The figure is a 1/35 scale Testors figure. Testors figures run on the small side.
While this wall won't work for a building, it will definitely work as a retaining wall or old rock wall or canal type embankment.
The rocks are of decent size and shape and detail.

Variety

As mentioned this line has a number of different ruins in it. This one is an old monument made up of columns.
The poly-resin can be cut so that individual columns can be used elsewhere or to customize them to fit your need.