Hi! I take it your just asking for some general suggestions? Here are a few that I've heard recently:

Christopher, William, Alexander, Charles, Christian, Dennis, Andrew, Troy and Brandon. Im having the same trouble picking a name that "goes" with the name I have picked for my next child (don't think Im pregnant at the moment, but theres always the possiblility) My son's name is Loki Alexander, but if I have another boy I dont know what middle name Im going to use! Girl names seem so much easier to me. Hope I somewhat helped, but I know what kind of position you are in! Let us know what you ultimately decide on, Nicholas is a very cute name!

General suggestions to start narrowing down would be -

Do you want a family name? Your maiden name or other last name in your family

do you want a name to link him to anyone else - your father's name, your husband's father's name, you husband's name

Do you want a "common" (as in frequently used) name or do you prefer to choose something a little more different b/c his first name is not very uncommon? I know people who chose the name of the place where they fell in love (the actual location winds up a tough name for a kid, but in theory...).

Is there any ethnic name you'd like to express your heritage? My friend wanted a more common English first name for her baby, but considered a Thai middle name to encompass her heritage.

Without knowing your last name (or you!), it's hard to pick more for "flow," but I hope that helped.

Our son is Nicholas Lawrence, but I also liked Nicholas Braedon, Nicholas Michael, and Nicholas Gage

Our son is named Nicholas Lawrence. I also liked Nicholas Braedon, Nicholas Landon, and Nicholas Michael

Nicholas Mark
Nicholas James
Nicholas Owen
Nicholas Patrick
Nicholas Robert
Nicholas Michael
Nicholas Eric
Nicholas David
Nicholas Evan
Nicholas Gabriel