About library usage and demo. For using SD library only, download sd_fat folder and stm32 folder from registerHeap repository, use makefile in sd folder for project building. For building a demo, add st7735 folder, and build the project from makefile in this folder.

This demo is written for stm32f103 with st7735 160x128 display, and can open only native resolution (160x128) jpeg files. If you wold try it demo, you can add your files on SD card and open them through showJpeg(char *fileName) function in main of st7735 folder. 

Pinout: SD card is on SPI2, display is on SPI1, all other pins, except of interfaces are defined in cmd_spi.h and st7735.h files.