National Instruments will not be implementing this idea. There is no further feature development planned for XControls.
When you create an X-Control the icon that you see is the Library's icon (as the X-Control inherits (indirectly) from Library class)
Usually this is just a banner as your icon is used to "group" and identify Library Member VIs (just like any other Library)
However, in the Palettes and Help it shows up like this:
Which is very uninformative (the main issue here is the Palettes) and not pretty.
If you were to go back to your X-Control Library and change the icon to a 32x32 image (e.g. something standard to represent the control) then this icon would propagate through your Library and mess-up/hide Member VI's icons!
Therefore, my idea is that, through the X-Control's Properties Dialog Box you should be able to associated the X-Control Library file with a custom icon.
Initially I thought linking to an external file (.ico or .png) would be good but now I think the above is nicer - storing it in the X-Control Library would be the best.
X-Controls are a special case because currently they are the only Library file that is can be added to the Palettes.
X-Control Properties Dialog, General Settings Subpanel (Concept):
Library Icon would then populate all Member VIs and have the same behaviour as any other Library's icon.
Display Icon would be used when viewing the X-Control file visually e.g Help, Palettes etc...