This might seem like a pointless aspect to some. But your room will reflect your personality, your rules and most importantly the culture of the environment. There are numerous things to take into consideration, ranging from the positioning of the desks, posters, physical objects, book shelves, storage cabinets etc.

In terms of desk arrangements, it will vary from class to class. Some students will benefit from working in groups, where peer guidance will set them on the right track, and where grouped with competent students, modelling practice and answers will improve their success rate. However, other students, the ones that are more concerned with social events and have difficulty staying focused will not work well in groups. These students benefit more from paired desks arranged in columns as it enables them to share their thoughts with others but not so much that they could be easily distracted. Alternatively, isolating such students could also work, but only in the short term. Do not consider isolation as a long term strategy.

Classrooms are supposed to be comforting, to an extent, and above all, inspiring. Posters, charts and visual aids are a perfect way to brighten up the room while keeping it subject specific and learning focused. Students will be distracted by these, temporarily, but once they lose their new appeal, will serve only as a gentle reminder of the topic and a comforting aspect of the classroom. After all, isn't it the appearance of the classrooms that we remember best? Try to avoid introducing new ones frequently, as this may be distracting. That being said, it is always good to keep them course specific. If you move onto a new topic or course of study, replace them so students can use them as scaffolding to build upon.

A great way to enhance the classroom community, is by displaying students works on the walls. This will be advantageous in two ways. Firstly, it will serve to motivate students to achieve well and complete their work in a timely manner and to a high standard, in the hopes that they will get their work displayed. Secondly, it ensures that students feel as if they are part of a community and that they are a valued member of the class. Remember, everyone likes to be recognised for their great work.

Subject specific objects, bits and bots are a great way to keep students interested and encourages them to become more inquisitive. These are particularly great if you can incorporate them into a lesson or as a show and tell on the subject and it's uses/significance in wizarding society. Examples would include sneakoscopes for Defence Against the Dark Arts, historical manuscripts for History of Magic and even rubber ducks and spark plugs for Muggle Studies. The possibilities are endless, and there is always something you can have on display for any subject area.

Book shelves, or even books in general, are a great addition to a classroom. They make for great resources and references should a student or yourself need it and it immediately acts to set the tone and function of the classroom, learning. The key to using this as a successful tool in your classroom is to ensure the books and material are subject specific, are relevant, at an appropriate level and are up to date.
Likewise, storage cabinets are also great for holding materials for class, as well as for student storage should they need it for project work etc. Remember to have rules for its use, and ensure that it doesn't become a distraction in the class, i.e. students travelling to and from, numerous times per lesson.

Ultimately, this is up to you. Do whatever you are comfortable with and what will work for your school and your students. Remember to keep school rules and guidelines in mind when setting up your room. It's also a wise idea to take into account how the students feel and react, after all, it is their attention you want to attain, and if your set up doesn't work for them, then it won't work for you.