I have the canvas/linen impression plate from PTI and use it a lot. Below I linked to a card that uses it so you can see if it's the one you saw elsewhere. I've never been sure which side is canvas and which is linen, honestly. I think this is the linen side. It's the one I use most.
Impression plates create a more subtle effect than EFs and sometimes that's a good thing. You'll see the canvas/linen on the full BG in Pool Party CS, and you can compare it to the strip of Pool Party running across the card that I did in the Cuttlebug Swiss Dots EF. Much more subdued effect.
You do need to get the rubber mat set to use the impression plates. PTI sells it.
Happy Birthday With A Mixed Bunch Pool Party