Here are a few ideas...
There are plenty of opportunities out there for van owners to use their commercial vehicle for courier work. This could be working for businesses in procurement as a haulier, or delivering parcels to consumers and businesses on behalf of a courier, catalogue or delivery company. More companies are depending on drivers who have their own van, rather than shouldering the expense of running their own fleet.
If you're willing to put your back into it, there is money to be made from removals and house clearances. If you've got a larger van, in particular, you'll be well placed to make a start in the removal business.
Die-hard bikers will be only too happy to buy their perfect bike from a dealer or seller on the other side of the country, but not quite so excited at the prospect of riding their new machine all the way home, especially if it's been off the road. All you need are a ramp and some straps to safely secure a motorbike in the back, and you've got a popular business on your hands. Charge either by the mile or by the job, and you should be able to earn a good wage.
"Man With a Van"
Or Woman With a Van, of course. Advertise your services and availability to do whatever people need, if they don't otherwise have access to a van. It could be collecting that sofa they bought on eBay or dropping off some rubbish at the tip for them. If it fits in your van, you can do it!
Believe it or not, you could make money from your van without having to put anything inside! Some companies will pay for the opportunity to advertise on your van. With lots of large surfaces, a van makes the perfect blank canvas for a mobile billboard, and in much the same way as a bus or taxi, you could offer advertising space. Equally, if you're advertising your own services, then your van is your shop window and it's worth investing in good quality graphics or even a vinyl wrap to make it stand out.
Similarly to motorcycle transport, there is always a market for specialist transport services, such as animals, pianos or even refrigerated goods. So look carefully in your area to see what services might be missing, and you might be able to corner a market.
Whatever you choose to do with it, your van is a great asset with a multitude of potential money-making uses, so make the most of it!