At 10.30am the huge poster was unveiled by TV star Ben Shephard, Harry Potter actors Oliver and James Phelps as well as other celebrities.
The board stands in Birmingham City Centre near to Selfridges.
The charity ball will be held at Birmingham's ICC in October and is aiming to raise over £50,000 for Help Harry Help Others, the charity launched by Harry's mother.
The ball is expected to be attended by many celebrities including England footballer John Terry, Dragon' s Den's very own Duncan Bannatyne, and television presenter Alison Hammond.
Harry's mother Georgina says she is overwhelmed by the support:
More than 50 companies in Birmingham have pledged to help out at the event.
Harry died of an inoperable brain tumour in October 2011, after spending his last two years raising money for charity by selling handmade bracelets.