The effects of the wish will disappear once the spell is broken, so anything created will eventually disappear at the end of the event. In the meantime, go for it as long as it doesn't break the setting.

Additionally (not relating to your character but just in case anyone is wondering seeing this in regards to limitations/power nerfs) any time or dimensional travel will not work because time is still frozen outside of Avalon. Using those types of magics will result in a character being stuck in frozen time, and they will end up being dumped back in the lake near the White Cliffs as a re-entry.