I think that there is expectation that pictures that will obviously be taken, but I'm not so sure about the shelves.
I don't think there is any expectation that holes will be filled and redecoration carried out, unless it is laid down in the conditions of sale.
As fixtures and fittings, they may be expected to be left behind, but it would depend on what was agreed in the house sale and what is laid down in the paperwork.
Certainly, items like gas fires and electrical fittings should not be removed, unless it has been agreed that (for example) an expensive gas fire or chandelier will be removed and cheaper items fitted in their place.
Check your paperwork and/or talk to to your solicitor.