Muslim cemeteries are all about minimalism and deference, so they don't have extravagant grave markers. A small marker or gravestone, however, is fine. Traditionally, you don't put anything for the deceased on or around the grave: This means no cut flowers, candles or other offerings.
There is some debate about whether women can visit the grave of a loved one to remember him. While some Muslims say that this is forbidden, others think it's OK to occasionally visit the grave site to remember the deceased and meditate on mortality.
Muslim tradition even has rules on how to console grieving friends and family, though these aren't as strict as some of the other funeral traditions.