Dance-mix Ending
Search the well in battle #5. You should get a ticket. Now win the game and wait past the ending. You should see some of the people in the game dancing around.
Excellent Mode
Turn on the game. When the SEGA logo appears, press DOWN repeatedly until you hear a tone.
Get lots of levels
In battle #14, in the center of the battle area, you will find a lizard man, a sorcerer, and an evil pixie. When you kill the evil pixie, it will keep coming back to life again and again in the doorway to the next battle. You can keep killing it over and over for more experience. To help kill it and keep from dying, put Graham directly over the doorway and shoot the evil pixie. Make sure Graham has the Robin Arrow from a previous battle, or the assault shell that you can get in the shop after Rhode joins you; it costs 2,200 gold. After a while, the sorcerer will run out of magic and he will no longer be a threat. But remember, once you kill all the enemies, the battle will end. So, keep the sorcerer alive until you're done killing the pixie.
Hidden Characters
As with all Shining Force games, this one has some hidden characters.