With over 1m businesses using Pinterest, I think that's a great idea and don't be afraid to be focused.

In my experience, your prospects will have 3 pain points you can address:

1. Creating and posting great photos in the best size and with the best tags to support findability. (+2bn searches per month at Pinterest)

2. Sustaining this (most businesses struggle to maintain their posting schedule)

3. providing lead generation reports.

And I'd also focus on businesses whose product or service offering is best communicated visually. (e.g. avoid law firms)

Good luck.

happy to advise.

Mark