Source Card Images
The card images are what is actually going to be printed, so getting print quality card images is essential.
According to u/Chilli_Axe the highest DPI that MPC can print is 800DPI, this means that the highest quality MPC can print is 800 pixels per Inch. The card size we are printing on is 2.48" x 3.45" so the card size should be at least (2.48 * 800) = 1984 pixels wide and (3.45 * 800) = 2760 pixels high.
If the image isn't at least 1984 x 2760 then you won't be printing at the best quality. This may or may not be a deal breaker but definitely something to keep in mind. Check out this discussion if you want to read more about image sizing.
The lower the DPI the worse it is going to look. Do note that it is NOT recommended to use anything lower than 300DPI (744px x 1038px). Even 300DPI can look bad and text will come out blurrier than a higher DPI equivalent.
Anything 300DPI or below MPC will alert you to the bad quality. Keep in mind anything above 800DPI is dead quality, the end product won't look any better after this point - the only increase is to the filesize (and therefore download time).
For this reason we will only obtain our images from sources that are at least 300DPI, luckily there are many options.
The easiest way to obtain the images you are after is to use Image Fetcher. You can literally copy and paste an entire sheets worth of card names from the excel sheet and into Image Fetcher. Start with the Artifacts column.
Next, select the 'variant' of each card you want, click download and wait.
Once you've finished each Excel column (and thus all of the cards) take all the images out of your download folder and put them in a new folder structure. Create a folder for each card type, for example:
Move all the artifact images into their respective folder. Continue this process until you have all of the images of the cards you require.
Lastly obtain a card back.