Well firstly you need to be clear about what the project is for. If it's a personal project, what are your goals? You obviously don't have any specific project in mind so I presume the goal of the project isn't to solve a real problem that you've actually got. Is the project intended to make up the basis of a class exam or assignment? If so, to what level must the finished project be acceptable?
These points mainly govern what type of project you're going to think about doing. If you're taking about a GCSE level project for example, then we're going to be looking at a design which challenges and satisfies the criteria laid out by the syllabus for GCSE Electronics, which in theory should be relatively simple. If on the other hand we're talking about a degree level project then we're going to need to look at a much more complex project which satisifes the degree subject syllabus.
Let us know some more details.
Brian