There are already several designs. One is in my profile. It is not my favorite, though.
The 51-star flag does not look as nice as the 50-star flag (or the 48- or 49-star flags). But we wouldn't need a 51-star flag if we go straight to 52 by also admitting a "State of New Columbia" comprising Washington, DC and its close-in suburbs in Maryland and Virginia. Admitting New Columbia as a state would enfranchise the residents of DC while simultaneously making Virginia an overwhelmingly Republican state and making Maryland a GOP-leaning state. See http://auh2orepublican.blogspot.com/2005/08/fair-and-reasonable-alternative-to-dc.html
A 52 stars on the flag would be in 4 rows of 7 and 4 rows of 6, and would look like this:
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Whis is not all that different from the 50-star flag:
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