I've received a few reports that the latest version of Custom Maps fails to load some images. Which is curious, as it relies on the Android system libraries to decode the image files. I have received a few jpg samples that fail to load for investigation, but I don't have any failing png images. And the others have reported that they manage to use the images if they convert them to pdfs first.
If the png image that is giving you trouble is not too personal and doesn't contain any sensitive information, would you mind sending it to me? It would help me troubleshoot and find what is different about the images that fail to load in Custom Maps.