The colors are ok, you're missing some contrast and the high's are a bit too low. the composition feels incomplete because, other than that render, there is no feel of continuity. The render looks apart from the background and that gives off a bad feeling of separation. You'd most likely want it to feel complete.
I am in no way near professional level of signatures, but here is an example from my own work:
Here is an old signature with simple background, just as yours, but with some level of intent, to focus on the main character (Puss) due to Depth of field):
Here is another one, my most recent work, in which I specifically use a rectangular shape to show separation, but it still retains some sort of unity. My bar is there to show depth in ways other than depth of field:
There's a lot of stuff you c ould have done there, The signature pales in content compared to that text. The text is supposed to be there to complete your work, not to be the one that stands out the most.
All in all, good luck.