I have tried many ways to fix it but the flash disapears when I change the fit type
You have width, height, and scale parameters. If set scale to - no scale, it won't break proportions. Or if you know original width and height set it.
I should also ask the author for a tiny enhancement. if the shadow under the box is made with respect to the image it is showing (which may be transparent in some parts) it will give the whole thing a great depth.
However the problem is it will shift the menu bar (in position-0 my_beez20 nature template) down and it is annoying.
I hope the developer continue his great work and correct the bug.
Thanks for reporting your issue, but I wish you had contacted me regarding the issue rather than post it here in the review. I try to be very responsive to errors or other issues with my extensions.
Version 1.1 is now available and resolves this issue - tested against the beez template.