I remember while using an old artrage version where the program crashed before fully saving my painting, causing me to lose my work. I think it might be a good idea to have a temporary file to write to before overwriting the main and maybe a one-project backup cache just for good measure. For the end user maybe Artrage could automatically give the user the option to try and load the last saved painting, but I think any artist would scramble over the technical headache just looking for a .ptg file called "backup".