Noninvasive visualization of living tissues is in great demand in the field of medical and biological studies. High resolution ultrasound imaging has made it possible to image small structures with fine spatial resolution and been widely used in the biomedical field including the dermatology, ophthalmology, intravascular imaging, and small animal imaging. The individual study is unique in nature and requires different utilization of the imaging system, such as different transducer characteristics, data acquisition strategies, signal processing methods, and image reconstruction, display and storage. Therefore, there is a demand for a flexible and open imaging system to allow users to customize the system for various studies and have full access to experimental data. In this paper, a real-time compact and open system is developed for customized high resolution ultrasound imaging studies. The system was based on high-speed field programmable gate array (FPGA) embedded in compact printed circuit board (PCB) to achieve flexible ultrasound imaging. The system structure could easily be modified by the users for customized applications. Testing results show that the system can offer a very flexible setting with B-mode imaging, modulated excitation imaging, Doppler imaging, intravascular imaging, and multi-modality imaging for high resolution biomedical applications.