Good fan-made mega evolutions can be hard to come by, but when you do, it is hard not to admire the talent of the artists involved and the thought they put into their work.
However, in my opinion, not all Pokémon should have mega evolutions. Though we may wish more existed (and more probably should exist), in some cases it over-complicates things for new trainers, and many Pokémon are already viable choices on their own. By all means, give weak final evolutions (or Pokémon that do not evolve at all) a mega evolution to boost their power and get them more involved at the competitive level.
Nevertheless, we should be careful what we wish for, lest we end up with less variety in Pokémon strength levels, or more mega evolutions that resemble Mega Camerupt. To be frank, Mega Camerupt looks like a Roomba, or some deranged alpaca.
Enjoy these interpretations, as in time, Game Freak and Nintendo will likely implement their own versions of some of these mega evolutions. Let us pray for Mega Lucarios and not Mega Camerupts.