This fixes the behavior in case of a cell tag and it changes the way how the default image is found: instead of looking at the last output of each cell, this now looks at each single output (starting at the end) and takes the first one that has a supported MIME type.
This is a continuation of #707.
This fixes the behavior in case of a cell tag and it changes the way how the default image is found: instead of looking at the last output of each cell, this now looks at each single output (starting at the end) and takes the first one that has a supported MIME type.