Well, the base game's engine does not support anything past 255x255. You may be able to open it in the editor, but it won't be launchable.
And HD couldn't go beyond 480x480 IIRC. Not sure about DE.
There's a patch for SWGB (the Star Wars AoE2) that allows launching larger maps, but it turned out to cause some extremely weird errors such as breaking wall placement.