Awesome. I'll give it a try and report back.
Here's the output I got:
dan@aria:~/.local/share/Steam/SteamApps/common/Hammerwatch/editor$ mono LevelPacker.exe custom_dan/
Scanning and reading files...
Unhandled Exception: System.IndexOutOfRangeException: Array index is out of range.
at TiltedEngine.Drawing.ResourceContext.ResourceNameFromPath (System.String path) [0x00000] in <filename unknown>:0
at ARPGLevelPacker.Program.WalkDirectoryTree (System.IO.DirectoryInfo root) [0x00000] in <filename unknown>:0
at ARPGLevelPacker.Program.Main (System.String[] args) [0x00000] in <filename unknown>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.IndexOutOfRangeException: Array index is out of range.
at TiltedEngine.Drawing.ResourceContext.ResourceNameFromPath (System.String path) [0x00000] in <filename unknown>:0
at ARPGLevelPacker.Program.WalkDirectoryTree (System.IO.DirectoryInfo root) [0x00000] in <filename unknown>:0
at ARPGLevelPacker.Program.Main (System.String[] args) [0x00000] in <filename unknown>:0
dan@aria:~/.local/share/Steam/SteamApps/common/Hammerwatch/editor$