Design area is 10 x 10 on stitch painted 18 count. Fear of working with a dark background? Here’s some thoughts.
Use a fine thread like petite silk lame braid, or strand able silk and do an open stitch. Sparkle or a slightly lighter shade of navy/grey/charcoal.
Avoid a thread that is an exact match, by choosing a thread with contrasting qualities either in color or texture allows you to track to your stitches.
Then by backing your finished piece in a dark color will fill in “voids” if you don’t love the open look, or again opt for contrast to offer an interesting background to the orchid.