As an example, the following macro just shows the generic question mark icon, with the tooltip as the macro name:

#showtooltip 
/usetoy [nomod, btn:1] Timewalker's Hearthstone
/usetoy [mod][btn:2] Dalaran Hearthstone

The weirdest thing is that it shows the proper icon when the macro is being dragged

There is something wrong in general cause the same thing happens to spells, icons just randomly disappear