Whilst reading the book, The Midland Hotel, Morecambe's White Hope
by Barry Guise and Pam Brook*, I came across a reference to the Seahorse mosaic in the entrance lounge as having been designed by Marion Dorn and created from tesserae and glass mosaic made by James Powell Ltd, in "silver and undersea colours".
The Seahorse is famously associated with this Art Deco hotel, having been incorporated into the original architectural designs by Oliver Hill and brought to being by sculptor Eric Gill. In 1932/33 Marion was asked to create a Seahorse design for the centre of the lounge floor, the design later being used on the hotel's crockery and glassware etc. (No clue as to who made the glassware yet - but if anyone comes across some with a seahorse and/or Midland Hotel Morecambe on it, please let me know!)
I'm assuming that James Powell Ltd is the Whitefriars Glassworks, so figured some of the Whitefriars' enthusiasts would be interested to know about the mosaic if they don't already.
There's a nice view of it on this page (3rd picture from the top): http://www.seasidehistory.co.uk/20s_30s_hotels.html
* Book details: ISBN 978 1 874181-42-2, published by Palatine Books, 2007