Help with correspondence and licensing an image for use on the web

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Hello. I've just gotten an email from someone interested in using an image of mine on their website and I'm not sure how to proceed from here.

The image in question: http://shaydethelemur.deviantart.com/art/Tribal-bunny-67417627

The email I received is worded as follows:
"Hello ShaydetheLemur,

I've been looking around for a good picture for my website and I came across your tribal bunny. I'd be interested to use this pic for my website. Would this be ok with you?"

My reply thus far is this:
"Before I agree to license the image, I need to know where it would be displayed and what it would be used for. I would appreciate it greatly if you were to forward along the website address so I can take a look at it.

Thank you for your interest in my work, I look forward to speaking with you further."

Now, two things. The first is a slight paranoia that, in not having a URL for this person's website, I can't properly track if they end up swiping the image and using it regardless of my consent to do so. (This is making me debate a) removing the image from my deviantArt gallery entirely or b) heavily watermarking the image after saving a copy to my computer.) The other is that I cannot for the life of me think of how to word a response indicating that I won't let the image be used without being compensated for it.

Any advice would be greatly appreciated. Thanks!