[EscaCsamas]

I have another query regarding clothes, can a person wear T-shirts for prayer?? Although it is best to wear shalwar kameez for prayers but thats just not possible all the time for instance offering prayers at work, university, in uniform etc etc.

If your t-shirt will keep covering all your 'awrah (without exposing your back or even worse) even during ruku' and sajdah, your Salah will still be valid; but obviously another "style" would be preferred.

Also if my clothes i.e Shirts usually, have small logo/ symbol/ picture/ writing that is visible on the side or on the pocket of shirt, can I offer my prayer in it??

It will depend on the picture itself and its dimension.
Any picture/image of living creatures would be at least problematical (it will then depend on its size).