hi sorry for late rely,
I will need some basic system info to tell what is the problem, Please make a github account (if you don't have one) and make a bub report here: https://github.com/mayank-prasoon/world-maker/issues. also mention which version you are using (current version is World Maker 0.1.1g)
Note: The maximum image size is 16384×16384 pixels due to graphics hardware limitations. Larger images may fail to import. so any thing beyond that will crash the system. Other than that the app uses multi-threading (different core) to load the image into the app so that can be a issue.