That is MUCH better than the current look so 
for a minor improvement.
Regarding general improvements:
I would agree that a major factor should be the icon’s ability to look good on both light and dark backgrounds and for a logo to have a design that has the same feel when using the version for either on light or dark background. Slack had to do a refresh of their logo and icon this year for this very reason. You can read Say hello, new logo | Slack.
I think color works really well though the current state of the logo is heavy on grayscale which isn’t that great on white or black. I tried reading through the 3D Slicer Visual Communication Guide to understand the background and usage.
- The lighter gray for “3D” restricts the ability of the “Slicer” text being white or black depending on the background. I think the text color needs to become the same.
- Maybe the “3D” part even gets dropped
. It does seem like the “3D” part is dropped in more cases than not including the domain “slicer.org”. - Dark support is also important when Slicer runs on macOS Mojave with Qt 5.12+ with macOS dark mode support (built with 10.14 SDK though deployment target could still be 10.12). Mojave is almost a year old and macOS Catalina will be out soon.