Sure you can download images only.

many ways of doing it also, with filters.
You can set a limit by image size and type (download only JPGS bigger than
20Kb and smaller than 1000Kb, for example)
download files based by name (nude_*jpg)
etc.
Read up on HTTrack filters.
It's a great image downloader , document downloader, or, yes, porn downloader.

Whatever you need it to be.