I really hate KYC. I have to effectively give my id docs and pics to strangers and I might find it in the dark web anyday. The only answer I have found to this is introducing a watermark, barely visible or sometimes clearly visible, indicating the ICO and date. If it leaks, at least it could be determined from where.
The problem of preserving one´s documents is a very wide one. There are a few projects that you may want to take a look into:
a) Selfkey
https://selfkey.org/ - "SelfKey is a Blockchain based digital identity system that allows individuals and companies to truly own, control and manage their digital identity, and instantly access Citizenship and Residency by Investment, Company Incorporation, Fintech Products, Token Sales, Exchanges and much more."
b) CIVIC, this is a well known one, which includes a "REUSABLE KYC Satisfy KYC requirements with Civic’s easy-to-use, private, and secure solution."
https://www.civic.com/I personally wish more ICOs would accept these, and I sure many will in the future.