Have you thought of introducing little knitted motifs onto your cards?
They do take a little while to do - but they are very popular for baby cards. I have not made them for a few years now - so I will have to get my needles out and make a few...if anyone beats me to it and would like to have their card on here send it along.
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Here are a few ideas to use up some oddments of wool:
Cast on 12 stitches (or thereabouts) and knit back and forth for about 10 rows - stopping in the middle of the last. Take a couple of cocktail sticks and glue beads on the ends, to make knitting needles. Then thread the knitting on to each of them. Leave some of the wool attached to make a 'ball' and glue this all onto a card. You will be amazed at the amount of people that think that you have knitted it on the little cocktail sticks, (I had loads of comments at craft fairs on these)!!

I have also produced a more grown up version to send to an adult - these used to go well on the WI stall, knitting is back in vogue this year so perhaps it is time to make some more.

The following ideas are all single sided items...after all they were being stuck on a card and could not be too bulky:
A boottee shape, I made a few holes along the lower cuff and threaded ribbon through, and popped on a bow, which decorated the top nicely.

I also did a stripey bobble hat with a ribbed cuff that I turned over, and made these in a variety of football themed colours. I then popped on a pom pom. I also intended to make a scarf - but never got round to it.

A knitted jumper, then add a felt head, legs and arms to make a 'teddy' wearing a stripey jumper. I must admit I did see this in a book first and it inspired me for other creations.

I used tacky glue to attach them to the card.

If you think of anymore ideas let me know.