At this level, Python's performance will make no noticable difference. For the majority of game projects, the performance cost of using Python is negligible; especially with computers getting exponentially faster every year.
The real cost bottleneck here is not language performance, but your own development time; especially as a one-man team.
It has a lot more expressive power, but if you're looking to ramp up the sprite count a lot, you might want to investigate a compiled language like C/C++/D/Haskel
The performance of software rendering is going to be garbage no matter what language you are using (C, Java, Game Maker, Python..). If you feel the need to put a ton of sprites on the screen, take advantage of hardware accelerated rendering through OpenGL/D3D (hardware acceleration is available on all of the languages mentioned in this post).