Is it against Apple policy / guidelines to create a custom button that links to the App Store, or does it have to be the official App Store Badge?
I believe you can only use the official badge. See the App Store Marketing Guidelines:
Use only the App Store badge artwork provided by Apple.
Do not modify, angle, animate, rotate, or tilt the App Store badge. Do not use the Apple logo alone. Do not use icons, logos, or graphics from www.apple.com to promote your app. Do not refer to iOS in your communications. Instead refer to the Apple products your app natively supports.
The Download on the App Store badge must be legible on all marketing communications in which you promote your app offered on the App Store. For all online communications, you must provide a link to your app on the App Store wherever the badge is used.
To add onto Yisela:
Affiliate Logo Guidelines and Art
The iTunes and App Store logos are recognized worldwide and using them correctly is an important part of being an affiliate partner. A few simple guidelines can go a long way in helping your partnership in the affiliate program:
- You must provide a link to iTunes or the App Store wherever a badge is used.
- iTunes or App Store badges should be used anytime the link is not a text link.
- You may never alter the artwork provided except to change the size. See guidelines for size spec and limitations.
- You may never use the Apple logo alone.
- The iTunes desktop icon, or other graphics from iTunes, cannot be used as a representation or link to the iTunes or App Store. iTunes, when used in headlines or text, is always shown as iTunes with a lowercase "i" and uppercase "T" even when it is the first word in a sentence. For the App Store, always capitalize "A" and "S."
Our badges are recognized worldwide. Proper implementation of badges gives your users clear direction on where to go to buy compelling content. Use the links below to access guidelines and badges for each of our stores.