FF6Tools - Browser-Based ROM Editor

The FF4 character graphics in the screenshot are actually from the SNES version, and yes you can import/export those. I haven't added character graphics for FF4 Advance yet.

For FF6 NPC graphics, there is a "Sprite Sheet" button at the top that opens a menu to select a different sprite sheet, i.e. "NPC (22-62)". The numbers indicate which graphics index should use that sprite sheet. NPCs use a few slightly different sprite sheet formats for special actions (waving, singing, surprised), so you will see some garbled tiles in places if an NPC doesn't have tiles for those actions. You should leave the garbled tiles blank when you import. It will automatically put the tiles in the correct places.