Don't be bashful! If you want comments, give comments. You don't need to be an expert photographer to express your opinion about the work of others. You don't need to go into great depth. A simple remark about cropping, composition, color, subject matter, etc. can be of just as much help to a budding photographer as an in-depth critique.
Photographing still lifes enables you to practice your compositional skills, and to create your own original image. In many cases, photographers set up their own arrangements, but life is full of still-life scenes if you look for them. The arrangement of a still life should begin with one dominant object, and others can be added one at a time until you feel that you’ve created a composition that works well. Don’t be afraid to experiment--there’s no single answer. As with all photography, remember that simplicity always works best. An uncluttered scene is often the most dramatic one.