Current release (v0.4.0.0) causes an exception at start:

IsolatedStorageException: Could not find file "C:\Program Files (x86)\Steam\steamapps\common\Kerbal Space Program\GameData\HaystackContinued\icons\button_vessel_spaceobject.png".

That file doesn't exist, and it isn't used, but it's referenced somewhere in the code. I just made a copy of button_vessel_unknown.png to get rid of the message. See forum: http://forum.kerbalspaceprogram.com/threads/89920-0-90-2015-01-17-Haystack-Continued-%28v0-4-0-0%29?p=1810635&viewfull=1#post1810635

But the best solution would of course be

• either provide this artwork
• or if it's not used, delete it from the code