Worst-case scenario: the UEd Goblin wipes the map and burns down your house.
From Unreal Wiki, The Unreal Engine Documentation Site
 Known Subclasses
Non-abstract subclasses of Texture appear in the Class drop-down list in the New Texture dialog that pops up when selecting Texture Browser Menu -> File -> New. (That includes custom subclasses, provided the package they reside in is loaded when UnrealEd starts by adding an EditPackages line to UnrealTournament.ini.)