I agree with this. It does look like you have some interesting pieces in there, but you do have a lot of potatoes, LOL! Maybe get creative with some putty and or cement, or some pegs. Also try and play with differences in elevation. Use the flat pieces to your advantage as those make great shelves and or bridges. Like you mentioned, nothing wrong with chiseling and hammering. You can use a flat ended screwdriver if the rock is not too dense. Also, gluing a bunch of liitle pieces together gives the freedom of getting more interesting shapes.
A lot also depends on what you plan on stocking with coral wise as well. Make sure you leave room for those to grow. The more branchy and outgrowing corals, the more room you need. That includes softies like leathers, nepthia, colt, xenia, Kenya, etc, LPS like euphylia, and of course most SPS will grow outward.
Its true you never know until you're there, but with all those little rocks, once you have an established coral load, its going to be extremely difficult to rescape. When I went from my 14 gallon to my 30 gallon, I thought I would have tons of space to mount my corals. Not so, I had to get creative even though I had essentially double the room. HTH.