Photobashing is a bit controversial as it is seen as cheating by many. Photobashing is not cheating as it requires skill and time to be done decently. Also, as long as you're having fun, peoples opinions shouldn't matter.
Anyway, to photobash is to pick different pictures and "bash" them together creating a complety new piece. You edit them a lot (emphasise on a lot) and you also draw your own things on top and underneath it all, it becomes a mish-mash of everything blended together. When the picture is finished it is often hard to see what's been drawn and what comes from a photograph or another picture. Photobashing is common among concept artists to Help them maintain a faster workflow.
We allow photobashing but you have to be allowed to use the pictures you're using. You can get by this by getting images from royalry free pages or using your own photographs/pictures.