I could not replicate the problem - the game file loaded up.
However, the image format of the dungeonwall image seems to be incompatible.
It seems the JPG file cannot be properly encoded, since I got this stacktrace:
javax.imageio.IIOException: Invalid argument to native writeImage
at com.sun.imageio.plugins.jpeg.JPEGImageWriter.writeImage(Native Method)
at com.sun.imageio.plugins.jpeg.JPEGImageWriter.writeOnThread(JPEGImageWriter.java:1067)
at com.sun.imageio.plugins.jpeg.JPEGImageWriter.write(JPEGImageWriter.java:363)
at javax.imageio.ImageWriter.write(ImageWriter.java:615)
at javax.imageio.ImageIO.doWrite(ImageIO.java:1622)
at javax.imageio.ImageIO.write(ImageIO.java:1588)
at de.gurkenlabs.litiengine.util.io.Codec.encode(Codec.java:135)
at de.gurkenlabs.litiengine.resources.SpritesheetResource.<init>(SpritesheetResource.java:41)
at de.gurkenlabs.utiliti.components.Editor.loadSpriteSheets(Editor.java:749)
at de.gurkenlabs.utiliti.components.Editor.load(Editor.java:328)
at de.gurkenlabs.utiliti.Program.lambda$0(Program.java:53)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Please try saving the image as .png and see if the problem persists.