I would do a satin stitch around the outside edge over the straight line stitching. I have seen how these fall apart after washing.
On another note, this image looks like a white lined sphinx moth. They are fascinating to watch. They are almost as big as a small humming bird and this long tongue rolls out to suck on the middle of a flower.
Here is a few pictures of them.
https://www.google.com/search?hl=en&...tuTzk#imgdii=_