Air = Flying - Valid. The Flying type covers everything from wind-based anomalies to attacks that would be situated with birds. (Peck, Drill Peck, etc.) Making an Air type would just be like making another type that's the same as the Flying type.
Gravity = Flying - I don't really agree on the match-up, BUT.. I don't agree that it should be a type, either. We've got Ground types, and there is even a move that is called Gravity (which is used by a Clefable on Victory Road) so making it a type would be quite useless.. and there isn't really much point to the type.
Magnetism = Electric/Steel - Very valid. Even Magnemite's line of evolution stands around magnets, "hence the name". On top of that, its both a Steel AND Electric type.. further proving the uselessness of a Magnetism type. It wouldn't fit in the games. At all.
Crystal = Ice - I don't really agree, BUT.. it would be a useless type. Its only really relative to an Ice type, because Ice is often portrayed as a crystal-like/gemstone-like structure; as was the case for the attacks; Blizzard, Icy Wind and Ice Beam, in Generation III. It might not sit as a direct link to Ice type, but it is just proved more pointless, by how it would fit in the game; it wouldn't.
Sound = doesn't make sense - Valid, once again. The moves fit a lot better in the Normal type, than creating a whole new type for them. On top of that, do I have to revert you to Whismur and the moves; Metal Sound and Grass Whistle? I doubt they would be "Sound" typed, just because they use Sound as their basis for attack. As previously mentioned, it doesn't fit in the game.
Plasma - Fire/Electric - So-so. Fire, not so much, but definitely very close to Electric typing. On top of that, Rotom is the "Plasma Pokemon", and it is part-Electric. Hmm.. that's pretty hinting, if you ask me. Plasma fits far too well with electric types for it to deserve its own type.
Light = fire/Electric - Again; so-so. Both emit light, however, a "Light" type, were it to refer to "Holiness" over actual light, would be the most viable type in the list, and to my knowledge, it is actually used by people, in a number of unique Pokemon games. but I will say its down to interpretation of the name, "Light".
..and stop it with the "These WILL work" comments. People are allowed their interpretation of things, if they so desire. Its like this post; I say it all, but a number of people will probably just ignore it. As is the world, I suppose.. *shrugs*