I figure that the Iguions were actual creatures once, that got petrified by some really strong magic in the distant past and thereafter used as decorations. There's not really much to support this, except for the fact that it'd be weird for Edea to waste time and energy on breathing life into pure rock, just for the purposes of a 'public show'. I just assumed she de-petrified the statues back into the creatures they used to be.

As for the Iguions themselves... they're half lion, certainly, but half reptile too - and aside from dragons, reptiles don't seem to be hugely important or symbolic in FFVIII's world. There is such a thing as reading too deeply into a text.