You can fill your skip with pretty much anything with the exception of a few items in this sitution common sense is the norm.
The skip must not be overloaded. This can cause problems when the skip is to be picked up and may also be hazardous to passing pedestrians and motorists. The skip should not be loaded above the top of the walls of the skip. If the skip is overloaded the skip hire company can reserve the right to 'level' the waste on picking up the skip if the skip is deemed unsuitable for transport.