Mulch or Bark?
There is a major difference between these two, I would recommend that mulch be used as this consists more of the tree such as the leaf and the branching of the tree and it is a great solution for holding water for the plants over the dryer months, also has a faster breakdown into the soil providing allot more nutrients and nitrogen in the soil to which plants need to stay strong and healthy. Bark does play its part to some degree more as a decorative aspect than anything else, and bark will over time draw nitrogen and nutrients from the soil and from the plants itself. My recommendation is use mulch, although will need topping up over time its a more effective and natural compliment to a thriving garden.
Stones, Rocks or Peebles?
This is more of a decorative attribute to a landscaped garden, also highly used throughout, they can create problems over time as wind creates dust and dirt to be blown about, this will eventually accumulate between the stones, laying a foundation of soil to promote the spread of weeds. If you feel you like to use stones or pebbles or rocks be well aware of leaf drop. This landscape material is better used for the more succulent type of garden a more of a dry arid aspect, to house the likes of succulents, yuccas, palms, and agaves. Remember when using stones these tend to get very hot and warm in the summer and can burn the base of many plants if they are fully exposed to the sun element.
For me weed mat is not my favourite thing on the planet, it is more of an environmental hazard than anything else. be very selective if you require weed mat in your garden as this can overtime spoil and sour the soil and also will not allow enough air, light and water to seep into the soil to access the plants root systems.
I know many of you use weed mat to prevent the growth of weeds. This is a false and has been proven laying a a thick layer of mulch on a garden bed plays a more generous part to the growth of the plants in your garden. Weed mat can sour and destroy important elements in the soil that a plant needs, so think twice before you use this alternative as a weed prevention.