There are different regulations for what is acceptable for gravestones per district. The possibilities are limited with community graves. With a personal grave though, there are fewer rules, but the regulations differ by district. Each district has a leaflet containing all the regulations on what is an acceptable gravestone. This leaflet can be obtained at the local city offices and is free of charge. Eulogy has a range of examples, for you to look at. Your local stonemason can also give you examples of ideas for shapes, materials and text. Keep in mind that even a simple monument can easily cost a couple of thousand of dollars.