It is better to talk for about 35-38 seconds. This comes with practice.
Jot down what you want to say first. Elaborate as much as possible. Could be an old building or a new one. Talk about the background of the image. Then what building as a symbol means. It means rigid tall structures symbolising strength. Maybe even say if it is a concrete or steel building. I am pretty sure there will be ample information to be dug out from the image. Usually the images are so produced that you can say a lot about it.
Make sure you prepare notes beforehand. This will help in fluency and content. Practice brainstorming about the picture a few times and you will start getting the feel of it and eventually will get comfortable and much better with it.
PTE – Academic Score: R-90 L-90 S-90 W-90 Overall – 90