Serving Tiles (with style) in 4326

The style has a list of layers - usually in an .mml or .yml file - and each layer has projection information to go with it. Since OSMBright is made for a database imported in Mercator units, and yours is in latitude and longitude, nothing will work - in effect, your data for the whole world will crouch somewhere near "null island" in the sea off Africa.

But all is not lost, you just need to inform your style that the data source is in EPSG:4326 instead of Mercator, then things will work again as expected. Look for layers configured to access the database with something like

"srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over"

and change that to

"srs" : "+init=epsg:4326"

BUT:

This whole exercise is only half of what you want. It is good that the style now knows your data source is in EPSG:4326 but you will also want to request tiles in that projection. It is no problem to use a command line tool like nik2img.py to create images in EPSG:4326 but all the standard tile generating programs like renderd etc. are geared towards the EPSG:3857 tiling scheme (where the world is quadratic). You'll have a hard time setting these standard utilities up to support non-mercator tiles because the assumption that standard mercator tiles are used is hardcoded in many places.