Design 101: Vector vs. Raster
In order to digitally create images for your Artist Shop, you'll need to use a graphics program. While most programs look like they all work the same way, it's important to understand the way they handle files and even artwork can be very different.
Raster-based programs include Adobe Photoshop, Corel Painter, Sketchbook Pro, and GIMP.
Images in raster programs are basically handled as pixels. Your image size is determined by the original size of your file as is the overall image resolution (DPI)
You can resize your files, but making them larger may cause pixelation and distortion of the image. Raster images are best for illustrations and paintings that would not require them to be blown up in size. Because of this, it's recommended you work at a larger size than your intended output. That way, if you find yourself in need to resize, you would be making your image smaller rather than larger.
As you can see, at 800% zoom the individual pixels for the design are very visible. Likewise, if you resize a design from 100% to 800% it would become even more blurry and pixelated. Unless you're making the designs smaller, a raster image not very flexible when it comes to resizing.
Vector-based programs include Adobe Illustrator, CorelDRAW, Inkscape, and Affinity Designer.
Unlike raster images, vectors are basically math. These images use points and curves to render sizes on the fly. Basically, vector allows you to create shapes that are infinitely resizable without any loss in quality. The original file size is not as important like it would be in Photoshop because you can resize the shapes you create to fit whatever your needs may be. These programs are particularly good for typography work and for graphic work.
You can see that at 800% maximization, the design's lines remain crisp and there's no pixelation, unlike Raster images. You can resize any vector drawing to be as small or as big as you want it to be without any loss of quality.
What Does This Mean for Me?
While both formats are flexible if you set your files up appropriately, creating your designs in one format vs. the other may limit what you can do with it afterward. If you're working with typography, you might want to use vectors in order to be able to tweak the size of your design to fit a large print as well as an image meant for the web. However, Raster programs like Photoshop work better for painterly designs that require the mix and blending of colors and effects and it is best to work at actual size or larger.
How you create your designs is entirely up to you and both types of images and programs allow for flexible and creative uses, so there's no need to limit yourself to one or the other, but it is important to keep in mind of the pros and cons of each type of image when setting up your work.