Is there anything that I can do while waiting for the decision on scholarship I applied for a PhD degree and has received an offer for it! However, I have to wait until next two months to know whether they give me a scholarship as well. I'm very nervous as the number of scholarships is limited and it's highly unlikely that I can join the programme without it. I am also applying for other universities as well but none of them offer scholarship covering everything for international student like the one I'm waiting for. 

Is there anything that I can do while waiting in order to strengthen my application?
The period between admissions and scholarship decisions is not really any different from the period between submission and acceptance notification.

If you have any major changes in your status—if you receive a significant award ("Best paper," teaching award, or similar), or if you have made a notable research contribution (published a paper, or at least submitted one), then that would be relevant information for the department. Otherwise, you'll just have to bide your time.