Do you have some quick tips on how to make a nice image with a makehuman toon?

Making a nice 3d image takes skill. There is no way around it: You’ll need to know what to do, and be good at it.

However, there are also some basic pointers which may be helpful when starting out.

Consider using a specific proxy for male/female (it particularly helps with the clavicle in female)
Set the “default no toes” skeleton in MH before exporting
Export/import using MHX2
When importing using MHX2, override presets and set rig to “exported MHX”. This way you get good weight painting and IK.
Use the cycles rendering mode in blender
Enable at least two subdivisions on the body at render time
Use lots of light with at least one narrow direct light source to provide interesting shadows, and plenty of indirectly bounced light in order to make things not too sharp
Do not use light capping or filter glossy. Using these shortens render times significantly, but it also removes crispness from the final render.
Increase light bouncing to the preset “full global illumination”
Consider mixing in SSS in the skin texture. Follow a tutorial from youtube to get a decent node setup
Read https://support.solidangle.com/display/NodeRef/skin to understand what else can be done for skins
For materials on clothes and surroundings, consider using PBR rather than the normal diffuse-glossy-fresnel mix. See https://www.blenderguru.com/tutorials/pbr-shader-tutorial-pt1/ for an intro. There are plenty of plugins/materials to download, so you don’t have to design them yourself.
If you got lots and lots of patience, consider using particle hair. See http://www.blendernation.com/2016/08/09/blender-cycles-hair-tutorial/
Most of what is true for photo composition is also true for making a good 3d still image, see http://www.techradar.com/how-to/photography-video-capture/cameras/10-rules-of-photo-composition-and-why-they-work-1320770