Try as I might, I cannot force the bitmap to show up any gaps at any scale on the design page or in Preview.

What I did was take your bitmap and cropped it to the first edge that was of a flower (non-white).

Once cropped on all four sides, I took a bitmap copy of that.

I cloned and flipped horizontally, took that pair and cloned and flipped vertically.
I then butted these all together, reduced the overall scale and took a final bitmap of them, which became my Pasteboard background of Flowery.xar

Acorn