This attorney will remind you to read and comply with the lease. Chances are that your lease allows the landlord to show the apartment. BUT he MUST give notice (the parameters may be defined in the lease) and you may reject a showing time by offering an alternate time that is convenient.
When it comes time to sign a new lease insert language that says no showings on Shabbos or yuntif. Chances are the landlord will agree.
If you repeatedly refuse showings and cause the landlord to lose a bonafide renter you may find yourself in court being sued or the economic loss.
If you are concerned about pictures and your privacy, take a set of pictures with those items removed and offer them to the landlord to duplicate for prospective tenants.