For picture composition:
-The min. required amount of words needed in each sentence (you need 5 sentences) is three. Therefore, you DO NOT have to make complex sentences. 
-The first sentence must start with "asmin chitre".
-There is a general template used in all picture compositions to get optimum marks:
Unless you know sanskrit fluently, DO NOT focus on explaining the scenario. Instead focus on the surroundings, and the simple things that are happening.
-Use bahvaha (many), and numbers.
-For example, if there is a teacher, 4 students, and 4 trees, your answer should be like:
1. Asmin chitre, bahavha vrikshah santhi.
2. Bahavah chaatrah santhi
3. Chatvarah vrikshah santhi
4. Chatvaarah chaatrah santhi
5. Ekah aacharyah asthi.
-Brush up on your numbers, lakar, vibhakthi, and (as) table.

4 3 4