Global Custom Visualizations
It would be very useful to save imported custom visualizations globally. For example, I enjoy using the text filter quite a bit and would like to save it without having to reinstall it from file or marketplace. If there was something akin to add-ins for excel this would be very useful.
Gradient bars
I would like to have a gradient background from one color to another across bars. I know I can manually add colors with the data colors section, but it would be great to have some kind of gradient from green to red or something.
Desktop Maintain formatting pane
When I select a visual on a duplicate page, have that same visual selected and the format pane to be still open. For example, on a tree map I'm making sure that every tree map is the same size and typing in x/y coordinates, etc and it would be very useful to have them all maintained.
New Look Feature for Desktop
For Power BI Desktop to get a good visual feel of the presentation please provide a view that mirrors the new look on the service. When designing complex interacting visuals it's better to see how it will actually display to users.