Use suitable linking words
Be prepared to use words and expressions that describe similarities – in both pictures, differences – but, whereas and comparatives to organise your answer.
It is important to keep talking in Part 2 for two reasons. Firstly, the examiner has given you one minute to speak and they will not interrupt you until that one minute has finished. Secondly, if you do stop it can be more difficult to start speaking. So continue talking until the examiner tells you to stop.
Answer the second question
As far as possible give a complete answer to the second extra question. You should speak for about 25-30 seconds in your answer.
Speculate about the photographs
Sometimes what is happening in the pictures is not always clear to candidates. So, it is absolutely fine to guess what you can see by using may/might/could. It can often be a very good way to make your answer longer.
While some candidates can find this part of the FCE Speaking exam stressful just remember is is only one minute and that you still have a lot more time to demonstrate your level of English.