If you are a proficient artist you could paint the canvas and give the canvas & easel as a gift itself.
I, however, am not that accomplished an artist. My suggestion would be to find a copy of your friends favourite picture and glue it onto the canvas so they have a mini version of their favourite picture to display. PVA glue would be ideal for this job as you can coat the top of the picture to give it a varnish like finish. Once the picture was dry, I would then superglue the canvas to the easel ensuring the easel can still open fully and stand.
You can write a gift message over the painting if you want this to be purely a gift tag. Alternatively you could write on the easel or use a luggage tag to attach to the easel.
I'm a massive fan of a gift boxes so I would attach the easel to a gift box making sure this could be removed with no damage. You could also thread a ribbon through the easel to hang on a larger gift.
These mini canvases would also work work in a children's party bag or christmas stocking for budding artists!