code: public ResultList<Artwork> getEpisodeImages(int tvID, int seasonNumber, int episodeNumber) throws MovieDbException {
          TmdbParameters parameters = new TmdbParameters();
          parameters.add(Param.ID, tvID);
          parameters.add(Param.SEASON_NUMBER, seasonNumber);
          parameters.add(Param.EPISODE_NUMBER, episodeNumber);
  
          URL url = new ApiUrl(apiKey, MethodBase.EPISODE).subMethod(MethodSub.IMAGES).buildUrl(parameters);
          String webpage = httpTools.getRequest(url);
  
          try {
              WrapperImages wrapper = MAPPER.readValue(webpage, WrapperImages.class);
              ResultList<Artwork> results = new ResultList<>(wrapper.getAll());
              wrapper.setResultProperties(results);
              return results;
          } catch (IOException ex) {
              throw new MovieDbException(ApiExceptionType.MAPPING_FAILED, "Failed to get images", url, ex);
          }
      }
docs: Get the images (episode stills) for a TV episode by combination of a
  season and episode number.
  
  @param tvID
  @param seasonNumber
  @param episodeNumber
  @return
  @throws MovieDbException