Back then in ~2011/2012 it was pretty usual to use MCEdit to transfer objects into other worlds.
Can you still use this tool? I remember some issues, if you hadn't updated it to the current version of Minecraft, but I saw that the last update of MCEdit was in 2013. My last world got messed up after some time (weird biome-generation and stuff) and I wondered if this may be because of MCEdit.
Or do you have other recommendations? WorldEdit is not an option for me, since my server doesn't run Bukkit. I would like to use an external tool to modify my worlds.