Start with a search engine-Google is always the best bet. Make sure your key words are what anyone who might want to find art online would look for,e.g. ‘online galleries’ or perhaps ‘paintings for sale’.
You’ll find a host of websites that offer different things. Some, such as http://www.britisharts.co.uk , will create a free listing that can be used to direct visitors to either an existing website or enable people to contact you.Although basic, directories can be extremely good for marketing if they have large numbers of visitors.
Many websites allow you to offer your paintings for sale but make sure you understand their terms. Some are free on a limited basis-they might have an image upload limit for instance- but do check. Questions to ask include: Is there an annual fee? How much commission is charged? How many pictures can you upload? What other information can you include? Is there a feedback or forum option?
Don’t forget to consider the design-the simpler it is to use,the better for all concerned. Make sure you know how hard it is for people who have found you to actually buy something from you. If paintings are grouped by subject matter or price, classify carefully. Remember also to note what is on the home page.If a common gallery has a ‘featured’ artist, how do you become one,and at what cost?