Can I be transparent for a minute?
When deciding on an artist to hire to paint at your wedding - your WEDDING.. one of the most memorable and important days of your life - there are a few things to take into consideration: availability, budget, and personal style.
If you and your spouse-to-be have talked about how cool it would be to have an artist at your wedding, do some research! Don't wait until two months before the wedding to ask around and see who's available. Coming from someone who is immersed in the wedding painting biz, trust me, we can only be in one place at one time, and the popular seasons (Mar-Apr & Sept-Nov) book up QUICKLY. It is extremely unsatisfying to have to tell bride after bride that I am unavailable for their big day. I'd advise requesting quotes as soon as possible. This requires no commitment, and gives you options.
Second, make sure you are prepared to fit this form of hired entertainment into your budget, and pay the artist what their time is rightfully worth. This cost can vary greatly, depending on who you're interested in hiring. While there is some natural competition in this arena, generally artists are confident in their work and firm with their price ranges. One example of the cost differentiation is the length of time an artist has been developing his/her style, and the general popularity of their work. You may expect to pay more for a well-known local artist, than one who has only a handful of weddings under their belt, regardless of how talented you think they are. This brings me to my final consideration, style.
No two artists can create the same exact style painting, especially under the pressure of painting it live. SO. Whilst doing your initial research, really look at each artist's body of work, and go with one that you really like! You might be drawn to trippy, abstract oil paintings, or maybe you prefer more colorful, impressionist styles. Some artists can create a realistic painting that makes you feel like you are in the room, among the wedding guests, and can see definite recognizable faces. No matter what, make sure that you are as confident as the artist that they will produce a piece that you will gawk over for the rest of y'all's lives, because, in the end, you are commissioning a painting.
I hope this insight has been helpful, and that you will be much more at ease with the process of hiring a live event/wedding artist.