A royal patron: James I
Shortly after his arrival in London in May 1603, James I granted a formal patent to Shakespeare's company, transforming the Lord Chamberlain's Men into the King's Men. Royal patronage brought not only prestige, but also increased prosperity--the Globe became more popular, and consequently more profitable.
Along with the other sharers, Shakespeare became a Groom of the Chamber*, entitled to two sets of royal liveries* every two years.
More about the art of the miniature portrait in England during Shakespeare's time.
Footnotes
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Grooming chambers
Although they were not normally in attendance at court, the King's Men served as grooms to the Spanish Ambassador on his visit to England in 1604 to negotiate peace.
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Nothing to do with the liver
A livery is an outfit of clothing in the colours of the the master--in this case James I. The records of the Master of the Great Wardrobe list Shakespeare as the recipient of four and a half yards of red cloth for the coronation procession of James I on 15 March 1604.