I use Spelling City for vocabulary practice. You put in the words and the site puts them in several games. Also StudyStack.com - on this site you put in the word and the definition and it makes games but not as many as Spelling City.
How about creating flashcards using Quizlet or Study Stacks? Both have a feature for adding images to the cards and both allow you to play games, practice, test, etc. There are more types of games in studystacks than quizlet but both might work for you. There is a new site called Wordia that has introduced Wordia for Education. Wordia uses videos to explain the definition. What makes the videos different is that they are created by individuals and there are several different people defining the same word. If you sign up for an account, your students (or others in your school) could create a video defining the words.