Start with the final card shape in mind
A custom card can look perfect on a monitor and still print badly if the file was prepared without considering the physical card. Standard Magic cards are approximately 63 by 88 mm, so artwork and frames should be composed for that tall proportion rather than cropped from a square image at the last minute.
Build at a comfortably high resolution and keep important details away from the outer edge. Printing and cutting can shift slightly, which is why backgrounds normally extend beyond the intended trim while names, mana costs, rules text, and other essential elements stay safely inside it. If a printer provides a template, use its bleed and safe-area guides instead of guessing.
Protect text readability
Rules text is where many attractive designs fail. A detailed illustration behind low-contrast type may look dramatic at full screen size but become tiring to read across a Commander table. Check the card at roughly physical size before uploading it.
Keep strong contrast between text and its background. Avoid shrinking rules text just to preserve decorative space. Mana symbols, loyalty values, power and toughness, and small reminder text need clean edges. If you are preparing custom Magic: The Gathering proxy cards online, export a test image and zoom out until it resembles a real card in your hand. If you have to lean toward the screen to read it, revise the layout.
Check artwork, cropping, borders, and color
Use the highest-quality source artwork you legitimately have permission to use. Enlarging a small image does not create missing detail. It usually produces soft edges and visible artifacts in print.
Crop intentionally. Faces, weapons, focal objects, and important background elements should not be accidentally cut by the frame. Check that borders have consistent thickness and that full-art designs still leave game information obvious.
Color also deserves a final pass. Very dark artwork can lose shadow detail, while extremely bright colors may not reproduce exactly as they appear on a backlit display. You do not need to become a prepress specialist, but avoid relying on subtle near-black differences or extremely faint gray text to carry important information.
Inspect the exported file, not only the editor
Before uploading, open the actual exported file. Confirm the dimensions, orientation, crop, spelling, mana cost, card type, rules text, and power or toughness. Make sure no guide lines, placeholder layers, or accidental transparent areas remain.
One useful habit is to review the file twice. First inspect it enlarged for artifacts and alignment. Then view it small for real-world readability. If possible, print a plain-paper draft at card size. It will not reproduce the final material, but it quickly reveals tiny text and awkward spacing.
Finally, remember the distinction between a custom print and an official Magic card. A well-prepared proxy can be useful for playtesting or agreed casual play, but file quality does not make it tournament legal. The best preparation work simply makes the intended card clear, clean, and comfortable to use.