I'm also painting up my Spanish cavalry - both from Magister Militum - to represent the large and small shield cavalry (except the Magister Militum don't appear to have shields, so I'll have to let the numbers / base illustrate the point...).
Clearly the scutarii (named for the large shield they carried - the scutum) form the bulk of the army. This consists of 3BG's of medium foot Iberians and 2BG of heavy foot Celtiberians. As I'm using the same model for each, I've had to use colour to differentiate. So the Iberians are in white with all shields having a black / white / red motif while the celtiberians (to represent the closeness of their Gallic chums) are more colourful with an emphasis on green / yellow.
Typical scutarii - mine will look nothing like this!
Both are Impact Foot so I'll have to use them as the Gauls - wind up and let them go. Their power is in numbers - 5BG's of 8 bases means a lot of units with Impact potential.
The caetrati (with javelin / light spear combo) in 2BG's should see off most opposing skirmishers and can provide some cover against horses and especially elephants.
The rules have tried to illustrate the Iberian scutarii's ability to be mobile in tricky terrain and on a battlefield with lots of difficult terrain they should pose the Carthaginians a problem or two.
I estimate a couple of days painting is required to finish them off so they may get an outing next week.