If you want to do something new, do a database application related to your interests. If you want to do something "professional", try contacting a local business (or better yet, a charity) and offer to develop something for them.
If it's not practically useful, then it's practically useless.
Blindman's point is that it is easiest to model things that you are either familiar with (your interests) or are well defined (REAL charities & businesses). I would go with your interests since you are also likely to be more motivated in your work and you might even have a use for the thing once you have completed your studies.
If all you really want are ideas then look through the Yellow Pages (in the UK this is a directory of businesses), look around your house at things that you have collections of that you might categorise, think of the things that you do that you might want to store formal records of etc.
My current project is HR for a multi-national company, running on an operating system than I haven't used extensively for over fifteen years. The last schema that I built from scratch was time and billing for a highly regulated industry, with some bizzare reporting requirements that were dictated by legislation (so we had no part in designing the reports, an no prayer of creating them from any standardized package).
The problem is that you are looking for someone to do your work for you, down to even picking your project. If nothing interests you, and you can't even be bothered to pick a project from thin air, I would strongly suggest that you re-evaluate your choice of careers. DBAs work long, hard hours. DBAs build the foundation that everyone else in the custom software industry works upon. If you have no interest and no passion for creating things and doing them right, then you might do better in another area.
my mind is blocked...do u know why i am asking u for ur help coz i can do many projects in database it is not a big deal for me ..but i am searching for something totally new...now u got whats in my head...