increasing the size for publication types as preview image substitute

[Robert Jäschke]

Currently, in the Bootstrap layout the images identifying the typo of publication do not fill the complete area:

as it is done by the preview images:

This makes it more difficult to identify the type of publication. I would suggest to adjust them to the full available size.

[Robert Jäschke]

I hope it's not too complicated. I wonder why it's not the default anyway.