Ref sheets allow you to have a standard reference for future commissions, particularly useful with fursuits.
Most ref sheets come without shading, and a colour palette to allow artists to pick the exact colours you prefer.
They tend to have a front and back view, sometimes a side view, which is especially handy for complex markings that can be tricky to understand from certain angles.
For ref sheets, my default option is a front and back view with closeups of parts you might noe see added extra no cost (Close up of eye detail, inside mouth colour, footpawpad colours if feet are down). You can ask for more!