I have never heard of a limit on number of indexes on SQL server. Basically, so long as you can create a unique name for each one, it should allow you the index.
However, it is never a very good idea to have a lot of indexes, as every time you update the base table, SQL server also has to update the indexes, and if you have many, the overhead will make your updates and inserts very slow.
If you want more than 5% of the data returned, or if there are less than 4 possible values for a field, it is really worth creating an index??
Tim