http://www.wipo.int/edocs/lexdocs/laws/en/dk/dk091en.pdf is the Copyright Law in English for Denmark. You should probably try to find a Danish version to ensure the translation is accurate.
Chapter 2 lists the exemptions from the general rule that you need the copyright owner's permission to use their IP.
Unfortunately, the usage you have made does not meet the requirements for private use (s12): digital copies may only be shared among the members of one household, placing them on the web extends beyond your household.
It may meet the requirements of educational use (s13) providing that your school has met the requirements for Extended Collective Use (s50). For photographs, this seems unlikely, such arrangements are usually limited to songs and television works.
Under Chapter 6b, you are permitted to use "orphaned works", however, this requires that you have made a diligent search for the owners and have been unable to either identify or locate them.
Copyright violation is subject to both penal sanctions (fines and in egregious violations imprisonment) (s76) and damages (s83).
Yes, you could be sued. Yes, the copyright holder would probably be successful. No, it is extremely unlikely they would bother.