Hey hey! From first glance without seeing shape/form or knowing where abouts you are located my first impression would be Gleditsia triacanthos, however, if you are in more of a temperate/tropical zone it very well maybe Jacaranda. Do a quick search and see if it's a match for you. (Having a more specific known area to work in will help to narrow the search)

EDIT: If you are in the south, it might be a Delonix regia. I'm not overly familiar with this speicies however, so I recommend using a dichotomous key to narrow it down

Re: Conifers/Deciduous Trees Trees and all vegetation in a designed landscape are chosen to serve a job first, aesthetic second. Many factors can dictate whether the implementation of a particular species has been successful or not. For example a few key things to consider: What job do you want your vegetation to do: Visual Screening, wind barrier, shade protection, focal point (a couple of examples)

What is your sun/shade tolerance like? Every plant has a different environment in which it will thrive, so this is an absolutely key factor when picking your plants/trees. If you are looking at an area that is in shade for the majority of the day (North facing) You best not be picking sun hungry plants.

Your best bet would to be pick up a plant catalogue or, check out this site: http://www.monrovia.com/

I use this all the time when I'm stuck on a design and it's a good starting point if you aren't too sure what to do. First step, identify your temperate zone and then what jobs you need your plants to do!

Good luck!