It seems that since 5.1 firmware (?) KT has a simple picture viewer.
Images have to be put inside "/images" folder (not "pictures" as on K3/K4), preferably in subfolders or zip files.
Then, the new item "Images" appears on the last page of the filelist (along with "Dictionaries" and "Periodicals Back Issues".
Unfortunately, picture viewer is very limited, there's no way to rotate or zoom in. You can only go through all the images in the folder.