Good start.
I think it would be bit nicer looking and more hand friendly if you had carried the spine back from the top without that dip.
Lay it on a piece of paper and trace the perimeter, then re-drew the top as one smooth curve to the butt. See if that doesn't look better. I can tell you it will feel and work in the hand better.
I know the "thumb ramp" seems like a great idea, but your thumb will sit in the same spot either way. If you are set on some sort of thumb grip, add small jimping or filework on the spine.
Another new maker tendency is to taper the handle up from the bottom at the butt, as yours is. It is actually backwards, You are best to taper the handle top down toward the bottom in an exact reverse of what you cut. In the sketch I suggested above, redraw the butt with the rounded tip-end on the bottom ( you can probably just flip the blade and trace the butt reversed).
Another suggestion would be to try and keep the plunge a bit more forward and crisper. You can make a simple file guide, or purchase one from any of the knife suppliers.
I'll try and post a re-drawn photo later tonight.
