I would like to mount the head of the Dino Triceratops, Item No: 4465c01, onto a brick/connector so it would be possible to fix it to a wall or over a door entrance. Any ideas on that?
I don't have this particular piece but my advice for most 'non-standard' connections such as these is to use a part that is flexible enough to fit the gap.
The 'Technic, Axle Connector Double Flexible' piece under compression can make a snug enough fit to mount a sharks head.
If you turn the rubber brick 90 degrees on it's side and place two of them together you might be able to attach something that isn't as wide.
The horn piece I have from an old castle set, and you can grab it with minifigure hands. I can't think of a visually appealing way to mount it by the horn,but it is still an option.