I have two weeks of time around Easter and was thinking to visit the region between the Caspian sea and China. I'm interested in everything (culture, nature, history etc.) and like to take photos. What would be an itinerary doable in two weeks?

You might want to take a look at some of the travel agency websites that put together Central Asian tours to get an idea of what is doable. I went to UZ last year, booked everything through Feruza at Advantour and had a fantastic time. You can check out my trip report under Uzbekistan. I hope to travel to Kyrgyzstan and cross the border into China sometime in the next few years so if you go, please write a trip report. It's a fascinating part of the world and I'm sure you'll enjoy

Thanks. How long did your trip to Uzbekistan last and how much did it cost?

I do write trip reports: http://www.molon.de/travelogues/
I have a recent one about Malaysia, Thailand and Singapore, which I'll upload over the next weeks.

Our trip was for two weeks and cost about $2600 for two without air. I will look forward to reading your trip reports - especially Malaysia.