Is there any performance difference in the way the images are placed inside a sprite sheet image (for the same total area)?
For example, should I place 50 sprites (50x50 each) in a linear way creating a sheet of dimensions 50x2500px? Or is it better to split into multiple rows, say 10 sprites per row, and get a sheet of dimensions 500x250?
Assume that the graphics are hardware accelerated.
It is possible that the total size of a sprite sheet will affect performance of your game in some reasonably small fashion. Extremely small sprite sheets generally mean that you have many, which in turn implies many state changes, and frequent state changes are not good for performance. Extremely large sprite sheets consume more GPU RAM, and if they need to be purged and recreated, or reshuffled due to resource virtualization of the GPU, this can cause a delay.
Keeping the same total pixel area and varying the dimensions of the sheet should not cause a noticeable variance in performance however.
As with most things performance-related, to determine whether or not a subject is actually an issue in your game you should profile it.
Put the profiler on it. Try a huge sheet and a small one. Measure the difference.
This is the very best way to answer these questions, since you don't want opinions: you want answers. Doing this test yourself is the best way to get an answer, since it will be for your actual use case.
Profiling is a good idea. You should remember you don't need real sprites. You could profile with noise instead. I personally think the shape of a sprite sheet is mostly a result of how we view it on a screen and the goal is too keep it easy to view so an extreme width is bad for that purpose.
I will also add that it is very unlikely the choice here will have a very noticeable effect on performance. It is always better to profile first before you decide what to optimize. Always optimize the part of the code that takes the longest amount of time to run until you are sure it is nearly fully optimized.
To optimize the rendering process of your graphic engine you should create sprite sheet with 2^n width and 2^m height (2x2 ... 128x256 ... 512x256 ... 1024x1024...)
Be aware, some engine like Corona SDK doesn't support more than 2048x2048 sprite sheet. Check the specification of your graphical engine. You can also use software like Texture Packer in order to optimize the arrangement of your sprite sheet.
