Higher resolution images usually reproduce more detail than lower resolution images. However, increasing the resolution of a low-resolution image only spreads the original pixel information across a greater number of pixels; it rarely improves image quality. Using too low-resolution for a printed image results in pixelation-output with large, coarse-looking pixels.
Bitmapped images are resolution-dependant, therefore changing the the size of the image can cause a loss in image quality and sharpness. In contrast, vector images are resolution-independent; you can resize it without losing its crisp edges.
The upshot is...if you must send bitmapped images, send the best resolution you have.
High Resolution bitmap (jpg) can be used for Silkscreen art with minimal artwork charge, can be used for embroidery setup (setup charge is quoted)
Scanned T Shirt or other garment, artwork charge required to turn into useable Silkscreen, can be used for embroidery setup (setup charge quoted).