There are two different ways to make custom Pokémon cards. Pokémon card makers are available online, where you can enter any desired information, including a photo, and generate a Pokémon card. For a completely custom experience, download GIMP, and then make Pokémon cards from scratch.
The easiest way to make your own Pokémon cards is with an online Pokémon card generator. Pokémon Card Maker, an online Pokémon card generator, allows a user to fill in attributes such as the Pokémon's name, type, hp, picture, species and more. Simply press Generate once all attributes have been filled in to view and save the customized Pokémon card.
Another way to make custom Pokémon cards is with GIMP. GIMP is similar to Photoshop, but is available for free for both Mac and PC. Download GIMP at Gimp.org/downloads. You then need Pokémon resources such as borders, energy symbols, fonts and type packs. These resources are available for download at PokemonCardResources.DeviantArt.com.
You can then import your resources to GIMP and design your own Pokémon cards from scratch. Once you have finished your card in GIMP, save it and export it as a PDF. For the full effect, print your custom card, and glue it onto a real Pokémon card. This way, the card will be the appropriate thickness and have the Pokémon card image on the back. Be sure to use a card you have doubles of and don't care about.