There are a lot of possible thesis topics you can work on. However, you have to take into consideration if the topic is relevant to your engineering major, if the project you are thinking is doable, if you have enough time to work on it, if the the overall cost is ok, and if your professor agrees to your proposed topic. Think of what you like to do best and from there start brainstorming for a good thesis. List down as many topics you are interested in as possible, then start filtering them out one by one... or you can consult the opinion of your professor about the topics you listed,