Hello I would like to use some Varangian guard in a Byzantine army. In the army list they are classed as short spear. Does this literally mean the model should have a short spear or would an axe or sword be suitable instead. Reason I ask is the models I was intending to use have axes / swords. Thanks.

You'll be fine - people are pretty relaxed about things and as they will, I assume, be "viking" type figures it will be obvious what unit they are. We define the troops as they are deployed as well so we aren't just reliant on the figures used 

That is great thanks.

Troops classed as "short spear" can be assumed to have thrown their spears before or during the charge into contact, and then be fighting with whatever supplementary hand-to-hand weapon they prefer.  It's quite common to see Roman legionaries depicted on-table with stabby things rather than pointy sticks, your intended Vikings will be absolutely fine