Hey there, this was my first custom from a few months back.
Just used the HoM Hulk as a base, painted it in red acrylic (sadly used cheap stuff since I didn't know any better, but I'm really regretting it now.) and used Citadel Foundation Mordian Blue for the jeans.
Sculpted the hair, but stupidly used enamel paint on it, so although it'd dried fine I lost a lot of detail.
Gave him quite a heavy wash so I decided to dry brush him with a brighter red.
The gun I believe started life as an Action Man handgun.

So there you go, my first attempt at customising. Made a few mistakes, but it's all a learning process, and the figure ended up looking okay in the end I think.