We no longer make boards dark so you do not need to worry about that. However there will need to be some variation in shades dark colours will be used for things such as the top bars. I presume you were speaking more on the lines of dark boards like Twilight currently is and if that is the case that as it will not happen.
Remember that the more you include, the smaller the characters will be. There are a lot of characters and many may be fan favourites or a favourite of certain posters but are they important to the overall storyline? Do you really feel that they must be included in the graphic? Or is it better to keep things simple with the main characters?
To be perfectly honest if you want to include one student then the question goes to all the others. If you include Neville then why not Draco, Luna, or any of Ron's siblings for example? I do want to make this clear that I am not a fan, although I have seen all of the movies, and I am not a poster here. I am also not saying you cannot include Neville or anyone else, it is purely my thoughts which I wish to share with you. You can do whatever you wish with them (including ignore them if that is what you wish to do) and I am not trying to start an argument, just make you think about who you
really want included. At the end of the day it is your board and we will do what you wish and it does not bother me one way or another. Obviously Harry/Ron/Hermione are the must haves and there is no question there. It is just the extras to consider
. How about Hagrid? He seemed important to me but is not currently included and is listed as a main character according to Wikipedia.
And for those curious the board was last customised in April 2010, with the customisation put up in June 2011 (which is the same as Daniel Radcliffe if you are curious about that was also). That would make it from during when the final two movies were being released. It has been a while but your customisation is only five years old which is what we hope for between customisations and the time frame we tell boards that they are likely to have their customisation for.