Your blocks are lovely! I especially love the dress block.
Here are two ideas for something you can do with a walking foot in the sashing strips.
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I have done both of these myself. The basic diamonds are easier. The diamonds connected with curves were complicated enough that I chose to draw them out on tissue paper (actually thin paper napkins) and then pin them to the quilt and then sew through the paper to do the quilting. (Removing every last bit of the paper was a bit tedious; Golden Threads Quilting Paper is supposed to make this easier.)
Your blocks are so lovely that you don't want the quilting in the sashing strips to distract from them - I suggest using a thread color that is pretty close to the color of the sashing fabric.
For quilting the blocks, I would be inclined to mainly do SITD and then do a bit of echoing in the blocks that have large spaces not covered by the SITD. My thought here is to not take attention away from the pieces of the blocks.