Need help! Metal shed building reception decor

How exciting, what a lovely free venue! It does look bright white, but you can certainly tone that down with strategic lighting. The biggest bang for your decor buck is uplighting which casts a colored light up against walls. It will also emphasize the high ceilings. You can rent these yourself and amber color is the most popular for events. You could even hang chandeliers and suspend from the garage beams. Or for a playful feel, hang a disco ball and project a spotlight.

To define spaces and warm up the industrial feel, you can bring in plants, or even potted trees to create corners. I don't think you have to spend money on a dancefloor as anyone can dance on concrete just like on grass. Instead, you can define the space by plotting plants or lanterns (or hay?) at invisible corners of the squared off area. Best wishes.

You can also define spaces with outdoor rugs, e.g. your sweetheart table.

If you Google "machine shed weddings" there are a lot of other pictures - here's one.