Post all your problems one-by-one and we'll identify whether or not they're really LMDE's fault, heh. Keep in mind that Debian and Ubuntu have diverged a lot over the past few years, and that not everything that applies to Ubuntu-based Mint will apply to Debian-based Mint. Try to keep an open mind...
Your current background/icon problem probably took place because nautilus-elementary from that 3rd party PPA probably pulled in additional artwork packages or whatnot as dependencies. Never used that PPA before, so can't say for sure...but make sure you purge
everything you installed from that PPA, not just nautilus-elementary. And hopefully you won't purge Nautilus and wipe out half of Gnome in the process...in that case, you have nothing else to blame besides user error.
