Here's a fun idea for a crewel project! How about a springtime garland? We love this vintage doily garland that Ravenhill did.
Why not have a crewel garland? I think some Appleton #992, #873 and #701 would look gorgeous on the natural plain weave linen. You could use the patterns posted here on Craftzine and do your own doily inspired look. Here is a little more inspiration to get you going!