Sound dampening seals on your footwear is a good idea.
You people need to think more outside the box with seals. Think of more non-combat uses of seals for ninja. ;)
What if you're a ninja assigned to a seduction mission? There could be a seal to prevent any... unexpected events that could arise over the course of your mission (alternately, slap it on a playboy so he doesn't end up having kids with half the village. "Sorry son, but if you're going to keep polishing your kunai with the ladies, we're going to need to take steps to avoid... uncomfortable situations that would look badly upon the family" or "Anko, you're going to get this seal placed on you or...."
).
Possibly seals that act as listening devices, recording on a paper elsewhere what's being said. Or a mail delivery system of seals, where the 'inbox' seal is in a permanent location - like the Hokage's desk, for instance - and the 'outbox' seal is a mobile seal that would be used as if someone were sealing the mail into the seal. Of course, instead of being sealed, it would be transported to the other seal. I would say that the 'outbox' seals would be personalized for a specific user to avoid it being used by an enemy, and the seals wouldn't be handed out to many people. Or something like that.
Better yet, seals that have an encryption method built into it that can be used to quickly encrypt data. Plus the decryption seal counterparts to the encryption seals. For security reasons, the seals would likely only be blood seals usable with specific people. So when the Sandaime retired, they had to make new decryption seals for the Yondaime to use. Or something along those lines.
