As Eurovision song contest is for the EBU members all of them could actually take part from Libya to Algeria, from Egypt to Jordan. All European members with the exception of the Vatican City have participated in the Eurovision. Tunisia was rumoured to be ready (like Lebanon in 2005) to take part in the late 1970's but it never happened and has not been heard since. Liechtenstein, Kosovo and Kazakstan are all interested, if you believe the internet but none of them is a full member yet. Maybe one day they will join the Eurovision family?
Australia, an associate member, has always been very interested in Eurovision and broadcasts it every year. The wildest rumours some ten years ago said Australia was ready to host the show in Sydney Operahouse and pay all the costs in change of being able to participate! True or not? My guess is as good as yours. The latest wild rumour is the interest of Qatar. But then, they have bought the African sportsmen to bring them medals in the Olympics so why not Eurovision as well?