my sprite sheets (Sword Art Online)

[Hoeloe]

No. JPG is not good enough. JPG compresses the information using an algorithm based on Fourier wavelets. This means that it cannot be reconstructed perfectly (as that requires an infinite sum). The effect of this is that you get an approximation to the original image, and you get aliasing appearing. This is fine for photographs, but when you're working with pixel art, which focuses on precise placement of individual pixels, hence the name, this is not good enough. Upload it in PNG format.