DSF

think of it from your own point of view - you have had an item made for a personal event you are celebrating - and then find it being used to publicise someone else's business - thats the best way of looking at it,

If you email and say to the customer, i want to use a few items to publicise my website, would you mind if i used yours ? failing that, use family and friends, but never think of using peoples personal photos - they have trusted you with them for their personal use on your website - not to publicise you own business without permission

You can write it into your terms and conditions that you reserve the right to use their designs for your marketing purposes. This can include anything and everything you print - including people and copyrighted images

Good idea SG.