Students often ask me questions like: Can I use "ascend" instead of "increase"? Can I write "the graph portrays" instead of "the graph shows"?
My answer to the above questions is no. If you write "ascend" or "portray" in writing task 1, it will seem strange to the examiner. Those words are not appropriate for a graph or chart description.
Remember: the aim of the IELTS test is not to find 'original' writers; it is to see whether you can express your ideas clearly, accurately, and in a certain amount of detail. These are the skills that you need for university or work. Leave the 'original' writing to novelists!