ICO conversion dimensions

Currently, the ico conversion downsizes the dimensions of every converted file to 256x256 pixels. Personally, I prefer to keep them in 512x512 pixels. There should be an option to choose the dimensions.

There doesn't appear to be an option to change this default size in the settings as there are no customization options in the "To Ico" conversion preset.

Please add an option to specify the default dimensions, as well as an option retain the dimensions of the original images being converted to ico format.