The embarking profile has nothing to do with graphics, from the errors it looks like your civ cannot have steel axes (or steel at all).
To add creatures, check any graphics_***.txt file. There you can see an example how to determine the bmp/png file you read from (TILE:PAGE) and how to set up creature coordinates properly (starts with 0:0 for the first tile, first number = horizontal index, second number = vertical index; professions are listed in graphics_default.txt).
P.S. Here's an example from my mod:
graphics_example
[OBJECT:GRAPHICS]
[TILE_PAGE:FALLOUT]
[FILE:example/fallout.bmp]
[TILE_DIM:16:16]
[PAGE_DIM:20:20]
[CREATURE_GRAPHICS:DEATHCLAW]
[DEFAULT:FALLOUT:12:1:AS_IS:DEFAULT]
[CHILD:FALLOUT:13:1:AS_IS:DEFAULT]
1) Look, first string is "graphics_example", it's the name of the file. You can have multiple files which define graphics, but the first line should be the same as the file name (without ".txt")
2) [OBJECT:GRAPHICS] means that this is a graphics file.
3) TILE_PAGE:FALLOUT determines where the file is and how does it look and what's its name ("FALLOUT") to refer to in this file.
FILE: *** is a relative path to your file. Mine is in Dwarf Fortress/raw/graphics/example/ and is called "fallout.bmp".
TILE_DIM defines dimensions of your tiles. My tiles are 16x16 pixels, thus it's 16x16.
PAGE_DIM defines dimensions of your whole file. My "bmp" file is 20x20 tiles (thus 320x320 pixels because each tile is 16x16).
4) Then creatures follow. Each creature is started with [CREATURE:NAME], where NAME is the name of the creature. Then you list a number of states/professions of the creature (i.e. default,child,zombie/carpenter,woodcrafter etc.). Usually for creatures you need a default and a child tile (if they breed), and zombie/skeleton if they can become undead. Let's look at it closer:
[DEFAULT:FALLOUT:12:1:AS_IS:DEFAULT]
DEFAULT means that it's a default tile which is used in any case except defined later for professions etc. You can use CHILD under it to define a child tile
FALLOUT is the name of the file (defined in TILE_PAGE above).
12:1 are coordinates (so it's 13th horisontally and 2nd vertically, starting from upper left corner which is 0:0)
AS_IS is a coloring parameter, if it's AS_IS it has the exact colors of the tile, if it's ADD_COLOR, it adds a specific tint of a profession/state (blue for crafters, green for hunters etc. like in ascii), it's useful if you have a single grayscaled tile for a creature and want to have different hues for professions.
DEFAULT (last one) means a "state" or something. It may be GUARD/ROYALGUARD for military to define guards' colors; also it may be SKELETON or ZOMBIE to define those tiles.
If you have more questions, just ask.