I bought a Dresdon plate at an auction.I used black as the background.That quilt still one of my favorites.Those plates just popped.The edges were not so frayed so I was abel to use the regular applique stitch.I entered it the county fair and the comment I got was that I should have used a background fabric that was more fitting of the time period.Well,they used black as a background color back in the 30's,soooooo.Well anyway,I love the quilt and I also used all the red fabric that was with the blocks.And I love the quilt,which in my opinion is what it is all about.I think you should use black as a backgroundand also even if you need to make the blades smaller,torn the edges under and applique to the background. JMHO

This could be done in many ways but you indicated that you wanted to keep your Aunt's intentions there. I'd leave it like it is, and use a small zig zag stitch around each piece. If you go changine it alot you won't think of your aunt when you look at it which I would think would be the point of finishing them off. It looks good, just need to make it stable now so that it holds up.

Yes, leave it like it is. It was meant to be this way. Today we call it "low volume" and that is one of the new things that was "invented" recently. (Just gave the old a new name.) I like the idea of stabilizing, though. Many good ideas were given here.

This is the option I would use! Fast, simple and efficient! Some fusibles are so lightweight, hardly noticeable.

I'm for the stabilizer on the back of the plates and then a blanket stitch. They are lovely and you will have a priceless treasure hen you are finished.

Buttonhole stitch using black gets my vote. Good Luck.

I think the light background fabric is very nice.
A defining satin or close zig zag stitch around the blades would be lovely.

You have already had lots of great advice. I just can't help adding my two cents worth.....these vintage blocks are exquisite and a great historical story of fabric of that time. There is very real possibility it even has personal and family clothing in those blocks. I highly encourage you to be as authentic as possible when putting these into a quilt form. It would be a tragedy in my opinion to add rick rack or any other bright embellishment. But of course this is just my opinion. Again, they really are quite beautiful. Also you talked about not enough contrast. Google low volume quilts...they can be surprisingly beautiful.

I had been given about twenty dresden blocks a few years ago. They were dated 1938 and every one of them were outlined with black embroidery thread in a blanket stitch. That black thread really defined the dresden plate and made it stand out from the background.