Lonelymum, it's pretty easy to sell, but I have found that baby clothes only sell well if they're designer or desirable, such as Mini Boden, Gap, OshKosh etc, and in excellent condition, or really cheap. People can pick scruffy stuff up at jumble sales/ charity shops so why pay postage?
Sometimes it helps to "bundle" things together, e.g. 5 pairs of trousers, 7 babygros, BUT bundles are heavy and the postage can be quite a lot, so your start price has to be very low, to make people want to pay for the postage as well.
Photos definitely help. If you don't have them be meticulous with your descriptions- I personally never bid for something without a photo.
If you can, buy a few things on Ebay before you start selling.You'll get an idea of how things work, and if you pay quickly you'll get some positive feedback which will help you sell.Don't go wild when bidding, though. Always look at the P+P cost, and set yourself a maximum you're prepared to pay, bid the maximum (you won't pay this unless others are bidding against you)and walk away until the auction is over.
HTH