Customer retention activity

I am an online only clothing retailer

Ihave recently completed phase 1 of my customer acqusition campaign; this involved optimising my current site for search engines, PPC campaign and re-engaging with affiliates - offering an additonal 5% based on new activity in the first month. I undertook a hygiene audit of my site, so any new traffic that came through found the site good to use.

I am looking at my retention strategy at present; I feel that to keep my customers I want to make their website experience better, I am looking to add value through interactivity on the site. I am thinking of building the functionality so if someone buys an item they can add other items to see how this will look on screen. will of course do the basics like send opt in e-mails to customers to offer them a discount on purchases. Enhancing the website seems the best route.

What other tools or activities should I be looking at. Research?

 Please advise.

Richard