In all the years I've worked, at several different IT companies, I've received numerous requests from various HR/Corporate communications to "please now use the following signature" or "please add this ... to your signature". I've ignored every one of them. No one has ever followed up with a message saying "Nick, you must use the signature" or something like that, nor even followed up informally over coffee.
To this day, I still sign off with "Regards, Nick"; though I will add a little more (like my surname, job title, and company name) if I'm making a new contact with someone outside the company.
Also, like mhoran_psprep suggested, the signature can get mishandled by some mail systems. One customer I dealt with recently had a complex signature that got broken down into several separate image attachments - the company logo, the regulatory body logo, the Facebook logo, the Twitter logo, and so on. After it had been round several different persons, a mail would arrive in my inbox with about 20 attachments, many of them multiple copies of the same logo! Pretty annoying when they also attached something important and relevant to the purpose of the mail.
I think you should just try ignoring the request. If really forced into a corner on this, offer an anonymous, generic image like suggested in other replies, or take ages picking the 'right' photo and hope they forget all about it.