This game has a lot of unlockable stuff but getting there is a real pain. You have to obtain S ranks in every stage in both the score and time areas. You don't have to achieve them both at the same time but there's a time section of your score so you almost have to do both at once.
Below is the original title screen on the left. The middle is the screen you get when you clear the game and the far right is when you get a 100% clear.
Kinda looks like they ran out of ideas for the 100% one. Hmm.
Next you can get several unique costumes by completing various conditions. Star Bomber from Land Touch 2 can be earned through certain milestones such as defeating 1,000 enemies or placing 10,000 bombs. Fairly easy. Cap'n Boom from Land Touch 1 can be obtained at certain percentages. You get a part when your files reaches 60%, 70%, 80%, and 90% respectively.
Cute Pink's costume is obtained by earning S ranks in entire Zones. I love the angry Bomberman face there lol. Finally Max is obtained by getting S ranks on every single stage. It's very tough and I cheated to get them all. It was so frustrating I'm not even mad lol.
As far as I know, Cute Pink is the only one with a distinct ability. Her ribbon can destroy soft blocks.
It's interesting how they tried to tie in the Land series at the time, even going as far as to call Pretty Bomber by her Land name Cute Pink.
Another cool thing is when you reach a 100% clear you get a unique ending. I won't spoil it but you get a special credits sequence where you can see many of the game's art images in full color with no text across them. Here are some of the more interesting ones.
And on a final weird note, here's the weird enemies from Practice Mode. They look kinda like jelly monsters from an RPG or something.