IPhone 6s case/cover picture dimensions?

I'm getting a case made for my new iPhone 6s with a picture (making a lyric edit). What are the dimensions for a picture that would work to cover the entire back of the phone?

Is 16GB enough for an iPhone 6?

Is it? I'm planning on buying the iPhone 6 brand new for £410 at my local store but I'm thinking it's not enough, I was thinking I could store all my photos and music over the cloud e.g Google drive. I don't really game on mobile phones and I only really need a few social apps and I could use some spotify for music, and can you store apps over the cloud along with music and photos?

Where can I get my iPhone 6 screen replaced?

My iPhone 6 screen cracked fairly bad. I have a lifeproof case as well, and it did nothing to protect it. If I'm not entitled to a free replacement from Apple, where could I get it replaced? (Website, tech store)

Random green pixels keep appearing on my iPhone 4s?

They are not dead or stuck or anything, because they are changing depending on what app is running. You can see them on certain shades (i can't really tell on what shades though) but it's super weird. Can anyone tell me what's happenning?
Also, i had my phone screen changed last Week…

Is this case the same color as the iPhone 6s in space gray?

So I need to get a case for my iPhone in the color "space gray" I then decided to get a mirror case. So I was looking on ebay and I see this,
http://m.ebay.com/...2058834177
So I was was woundering if there gray case is the same gray as the "space gray" iPhone 6s. I emailed the provider and asked but they have not respond so was I just wanted to see if any of you have this case and tell me if the color is darker, lighter or the same as the "space gray" color on the iPhone
Thank you for your time
God Bless

Added (1). the main reason why I'm asking this is because i want to see my reflection clearly and not to dark like i'm look at my reflection off my front screen i still wanna see some color to my reflection.