Anything to do with the historic Belgian Congo would be out the window. The peoples of the Kongo only have bad memories, and in the older age brackets- amputations (1), and the Queen would certainly not want to link the new Kingdom to the legacy of Leopold's Congo Free State.
The flag would likely combine heraldic references to both Africa and the House of Orange. Perhaps the Orange lions supporting a shield of the Zulu type- like in that link, emblazoned with recognizably African animal, like an Elephant's head. Or some mix like that.
Edit : Some poking around has found a "Royal Standard" Wilhelmina adopted in 1908, that could be the base for the UKN, while the Congo featured a Leopard's head for a bit, and a Rhino on stamps, no elephants. I may be able to cobble something together without too much effort.
(1)Historically, members of Force Publique were to supply a hand or ear for every round of ammunition expended. So you had a number of amputees.
Here's a quote from Wiki on the depopulation :
In the absence of a census (the first was taken in 1924),[9] it is even more difficult to quantify the population loss of the period. Casement's 1904 report set it at 3 million for just twelve of the twenty years Leopold's regime lasted; Forbath, at least 5 million; Adam Hochschild, 10 million; the Encyclopædia Britannica gives a total population decline of 8 million to 30 million.[citation needed]
This post has been edited 2 times, last edit by "Kaiser Kirk" (Feb 24th 2008, 8:56pm)