Here are a few ideas for tool party decorations. These are from Oscar's 5th birthday (duh.) Some pegboard with blue painter's tape makes a great sign. The painter's tape also conveniently disguises the slightly crooked edges that were left when I cut it with a box cutter. I used the Tool Shop Caps for his name. If I remember correctly I covered paper with the blue tape and then cut the rest of the letters out of that.
More pegboard, painter's tape, and a few pegs to hang the party favors on. I liked that this made a large wall decoration for the first part of the party. Once the boys were wearing their tool belts it was not quite as pretty. The favors for the kids were lowe's nail aprons with their names on them. They were filled with a tape measure and some tools for them to build with.
There was also bunting, balloons, and giant tools (poster board from the dollar tree and silver paint). Like I've said before, there is always paper and balloons for party decorations because they're cheap and add lots of the theme colors. And balloons are fun to play with.