I was wondering how Old Norse Christian names were usually spelled, and if someone has a list of them? The name I'm particularly interested in is my own; Mikael. I understand the typical modern Icelandic form is Mikjall or sometimes Michael (I think this is from English?), was this the same spelling a thousand years ago? Also, I'm Norwegian so I was wondering if perhaps Mikael is an Old Norwegian variant?
The Old Norse form of your name is Mikjáll, used in Norway since approximately 1350. In Sweden, the form Michael was used a little earlier (in the 13th century according to Otterbjörk).
I'm not sure about the English pronunciation at this early stage - if it was similar to today's English, it is unlikely that the name came to the Nordic countries via England. The pronunciation is much closer to the German pronunciation than to the English pronunciation. But, again, this is just a guess as I'm unfamiliar with the pronunciation of Old English.
At the moment we don't have lists of Old Norse Christian names, but it's a very good idea for future projects on Nordic Names.