Get image hosting first
There are lots of free image hosting services on the Internet today, but most of them are not reliable. Buy an image hosting that allows you to download gallery software. Gallery software will be best for your work as it makes uploading images and keeping them in order easy.
Image hosting service will provide you website with an upload interface. The upload interface will allow you to upload hundreds of images and create several galleries on a single website.
Search the Internet for most prominent image hosting services and choose one. Image hosting services also make it easier for you to share your uploaded images and photos to other people.
You can also use Photoshop to create an online gallery. Photoshop allows you to create, modify, and alter images. You can then use image hosting software to upload those images. Photoshop works best if you wish to run a big online art gallery. The software lets you create description of each image and gallery.
Ask artists to donate their work
Make a list of artists you know and ask them to publish their work on your website. It is not easy to get a famous artist to donate his or her work to you, as they make money out of it. However, you can still get in touch with many lesser-known artists who want to gain popularity by reaching more audience.
Do not steal somebody's work. Take permission if you have set your sights on a painting or an image published on a website.
Get in touch with professionals
If you are having difficulty creating your own online art gallery, you can sign up for websites that specialize in creation of galleries and artwork.