Graphic sets are relatively easy to make.I take it you already have your standard human? open him up in paint and give him an axe, then a pick, then a spear, until you have covered all the jobs, its advisable to copy paste your first blank human then keep altering him and pasting him again. I also find it useful to make a 16x16 box in paint i know my tile should fit in. The background for your tiles must be black or that magenta colour. (make sure all the "tiles" ie individual creatures are 16x16 pixels, and the paint file is saved as a 24 bit .bmp image), then save is at HUMANS Then go into raw/graphics (go into example and paste your beautiful HUMANS.bmp) and copy the current tile set raws you have for dwarves (this saves you a lot of work typing out)
then put in
[TILE_PAGE:HUMANS]
[FILE:example/HUMAN.bmp]
[TILE_DIM:16:16]
[PAGE_DIM:8:3]
[CREATURE_GRAPHICS:HUMAN]
[DEFAULT:HUMANS:0:0:ADD_COLOR:DEFAULT]
[---job name here---:HUMANS:--x coord--:--y coord---:AS_IS:DEFAULT]
[---job name here---:HUMANS:--x coord--:--y coord---:AS_IS:DEFAULT]
Put in the job names and coordinates for each job and set the page dimensions to whatever it is. Its ok to have black spaces. ok now boot up DF and see if it works. hooray.
Alternatively you could go into your existing graphics file (the one for your fancy tileset), and replace
[CREATURE_GRAPHICS:DWARF] with [CREATURE_GRAPHICS:HUMAN], then all your humans would use the dwarfs tiles. If you dont mind your humans looking a bit dwarfy that is