Slitherine

I am looking for suitable figures to use for Imperial German defensive spear Militia. I am looking at the period around 1200. What type of shields would they have? Round, large, or kite shields? Would there be a mix I am assuming?I am looking at Essex figures in particular, others possibly. Also any advice on shield designs?

Thank you in advance for your responses.

It depends...
Some Militias had issued equipment (not sure that applies to the early 13th Century though), but most were supposed to bring their own. So going for a wield mix is fully appropriate. Uniformity, if any, would only exist in most or even all bearing their cities device on the shield.

For the heraldry check on the current city heraldry (Wikipedia is a good start here), many city devices were established in the 14th or 15th century at the latest and did not see to much change since then. For the 13th century earlier it is usually difficult to be certain, but then that has the advantage that it will be hard to prove you wrong.

By 1200 round shields are a difficult topic. Generally they are probably a dated design in 13th century Germany. Yet they seem to have remained more popular in some areas (mainly northern Germany, especially in and around the Free Cantons and in East and Southeast Germany, possibly due to Slavic influence). So depending on where your troops are supposed to come from I would include some (especially among the protected spears if you use them) to almost none.