Royloo has a low priced bed that has the sheet on it  with wrinkles at 3-D Arena, it's not free but I don't recall a free one that wasn't dynamic either.

There is also an add-on pack that will morph the mattress quite nicely.

Daz also hasThe King's Chamber which includes a bed with messed bedding - PC item.

I'm assuming though that you want it to fit an existing bed?

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I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.
-Galileo