The dagger is interesting as an example of an imaginative design of what could be. What I am wondering is whether you are looking to make something historically accurate, or just an imaginative creation not closely based on actual daggers? If your desire is just to produce an imaginative design, then there's not too much to be said. If, however, you want something historically accurate, more comments could be made.
To my knowledge, there is no such thing as a "gallowglass" dagger. Rather, the gallowglass warriors would have used the same sorts of daggers used by other fighting men at this time. These include
ballock daggers, quillon daggers, basilards,
rondel daggers, and antenna daggers. For much of the 14th century, ballocks and basilards would have been especially common. Quillon daggers seem to have been more common at the beginning and the end of the century, and to my knowledge, rondels only start to appear in the later parts of the 14th century.
So, if you are interested in creating historical daggers, you should research 14th century examples of each of the various dagger types. All of these daggers continued to be used in the 15th century, but the style of their hilts evolved, which is why it's important to find 14th century examples. Likewise, 14th century daggers often, although not always, only had a single sharp edge, so learning more about blade shapes and styles will be of value.
You can find more information about ballock daggers here:
http://myArmoury.com/feature_spot_bd.html and more about rondel daggers here:
http://myArmoury.com/feature_spot_rondel.html.
Also, if you search 14th century images from Manuscript Miniatures
http://manuscriptminiatures.com/search/ , you should be able to find examples of basilards, not to mention rondels, quillon daggers, and ballock daggers.