Use brackets, hooks and nails to hang things off and clearly mark where each of your garden tools should be placed. If you create a home for each item, it will be easy to find and simple to put back.
If you’re mounting bikes on the walls, place them either one above another OR rest them on one wheel, with the other up against the wall. This frees up heaps of space, instead of having them stacked next to each other.
Surfboards can be placed in freestanding racks or wallmounted. Those used regularly can be propped up along the sides of the garage between wooden pegs. Mount them on rubber, behind a low barrier and secure with occy straps.