Your picture links are broken in your question…likely because the images were too big.
As for quality, check your texture import settings. As a starting point select your texture in your project folder and in the import settings use:
Texture Type: Advanced
Generate Mip Maps: Off
Max Size: Larger than your texture
Format: RGBA 32 bit
Note there are many settings here that have various impacts on size, quality and performance. In addition, since you are using a 3D environment with perspective, you will have to take additional steps if you want your images to be “pixel perfect”…that is to have a one to one correspondence between the pixels in the image and the pixels on the screen.