You have photographed this thistle beautifully. I like your viewpoint and the emphasis on the details of the flower's base, which is where the interest lies.
As to the frame...I frame a lot of my floral shots, especially, and of course they are a matter of taste. I think the heavily colored ones, such as v1 detract somewhat from the flower, but v2 and v3 are more pleasing to my eye at least. I usually choose a light color from within the image to use, and try to keep it from becoming too heavy. It all boils down to personal taste. You'll find yours, and if you like it, that's what counts in the end.