Q:

You better keep me clean, or you might contract a nasty facultative parasite

This one is going to be tricky:

There is a famous band with my name in it.
You better keep me clean, or you might contract a nasty facultative parasite.
I come in many shapes and sizes.
I have been featured in the background of a pic on charlie_swags instagram.
You can put me almost anywhere.
People neglect to use me when they think they are too cool for me.

A:

Are you annn...

 Air Conditioner

My reasoning:

 Band: AC/DC; Parasite from fungal spores; Shapes/location: window, car, central etc.; Picture: 4th image on this IG at time of posting.; No one thinks of AC when they are cool.

A:

Are you 

 A pool?

There is a famous band with my name in it.

 There's an American band called Drowning Pool which might fit the bill here...

You better keep me clean, or you might contract a nasty facultative parasite.

 The brain-eating amoeba, Naegleria fowleri, is a facultative parasite which can be found in unchlorinated (ie. unclean) swimming pools.

I come in many shapes and sizes.

 There are many shapes and sizes for swimming pools

I have been featured in the background of a pic on charlie_swags instagram.

 I hope it has been...

You can put me almost anywhere.

 They can be in-ground, above-ground, in-house, in the basement, on a cruise ship, on roofs, on any floor of a hotel, etc.

People neglect to use me when they think they are too cool for me.

 Too cool for the pool ;)

