Do not think that since you have not seen Lord Krishna, you cannot visualise Him. Do not worry that perhaps you will make a mistake. The merciful Lord Krishna gives us absolute freedom when it comes to visualising Him. Think Him to be tall or short; imagine Him to be fair, dark or blue. Make His hair short or long; curly or straight. Make Him a child, a teenager or an adult. Give Him a traditional or a modern look. Put heavy ornaments on Him or none at all; the choice is yours. The important thing is to think of Him as you chant.
.......SHRI MAHARAJJI.