It may be more useful if you can use both the synthetic/artificial/imposter and real world data. Here the, most important purpose is to test validity and performance of your proposed model/technique/algorithm/method. You can also use face database: https://www.robots.ox.ac.uk/~vgg/data/ or http://homepages.inf.ed.ac.uk/rbf/CVonline/Imagedbase.htm
The performance of any unimodal biometric system is dependent on factors like environment, atmosphere, sensor precision. Also, there are several trait specific challenges such as pose, expression, aging etc for face recognition, occlusion and acquisition related issues for iris and poor quality and social acceptance related issues for fingerprint. Hence, fusion of more than one biometric samples, traits or algorithms to achieve superior performance is an alternative way to achieve the better performance and is termed in literature as multi-biometrics or multimodal biometrics.
Refere the following link. It may be useful for you.