The Osprey on the Knights of Christ has a plate showing a spearman in the employ of the Hospitallers equipped in a basic fashion with the addition of a black shield with a white cross in the upper right corner.
This raises the question as to whether the foot hired by the Templars would have done the same? If so, then would the shield be white with the red cross in the corner or in keeping with the manner in which Templar Sergeants were equpped a brown of black shield with a red cross.
As the religious orders provided a significant proportion of the troops in Later Crusader armies I am painting up some SP for their contingent and it would be nice to be reasonably accurate with the shields.
On a further note, the Minifig Hospitaller Knight sigures are equipped with sugar loaf great helms. Based on the chronologies on helmet development this appears to put them in the period after the color change from black to red for Hospitaller surcoats and cloaks. THis also appears to make them more suitable for the later Knights of Rhodes.
I have no doubt that you are correct that the spearmen of the religious orders would have lesser forms of heraldry, such as small crosses dexter chief (in the upper right corner.) However, when painting my 15mm DBA Later Crusader army I thought that this would make the spearmen look rather dull, would detract from the look and overall cohesion of the army and with only 20 spearmen in the army I wanted to make them look good.
Then I consulted the authoritative archaeological evidence I was using (i.e. Ridley Scott's Kingdom of Heaven) I found I was fully justified using big colourful crosses everywhere...so that's what I did! Not a purist but the owner of a colourful Later Crusader DBA army!
OCD on my part paddy - wanting a historical feel for the troops (just ignore the various colors other than shades of brown I use on saddles and other tack...).
Interesting to see the Order of St. Lazarus getting attention for Crusader armies. Particularly in white with the green Maltese cross that was not authorized until the 1600s (there are even transfers...). Got me looking for the reference that stated Hospitaller colors for them in the Middle East. When I do mine I will use a green Roman cross rather than white to differentiate them.