I would not give them anything for free, because if you give it to them now, why pay you in the future?
That is the biggest issue right now as far as getting paid for photos in the industry, people giving stuff away for exposure.
Can you buy a McChicken with a photo credit? Nope.
Can you pay your mortgage with "exposure"? Nope.
If you have to give them something, limit the amount, make it non-high res, and make it social media sized.
I just had magnuson superchargers try to strong arm me for free pictures for their 2016 Calendar. Told them my fee, they all the sudden forgot where the reply button was.
Garrett Turbos screwed me last year, won't happen again. The only time I give stuff away is when its required in my contract for Power Automedia, and even then I'm getting paid to take the pictures by PAM.