BlueBrick only parses GIF images in the subfolders of the parts folder (see the Folder Organization for more details). The GIF image can contain a transparent color.
It doesn't matter in which orientation you place the top view of the part in the image, but to facilitate the integration of your part with LDraw, I recommend you to use the same orientation as the LDraw part. Otherwise, you will have to add remaping information in the LDraw section of the XML file.
The scale of the parts is 1 stud = 8 pixels. Since a stud is equal to 8 millimeters in real life, another way to memorize the scale is 1 pixel = 1 millimeter.
The names of the parts are not case sensitive, as BlueBrick converts all the names into upper case when creating its part library. Therefore if you create two parts that have the same name but with different cases, they will be considered as the same part. You can use any authorized character to name your parts (including spaces), but I strongly recommend you to use English characters only to facilitate the share of your map internationally. Also avoid using the period (full-stop) character since this character is used to separate the file name from the extension and is also used by BlueBrick to separate the part number from the color.
However since the filenames on GNU/Linux OS are case sensitive, the ".xml" and ".gif" extensions must be lower case in order for BlueBrick to correctly find the parts on Linux.
BlueBrick doesn't mind how you name your parts. The only constraint is that the name must be unique in the whole library. You cannot name two parts with the same name even if they are in different folders. Moreover this name becomes a unique ID that is saved in the layout BBM files. So to avoid naming conflicts in the library and to make your BBM files portable, one commonly uses the part or set number. This is just common practice, but I strongly recommend you to follow it. The official BlueBrick library will use this method.
Since there are some Lego© parts and Lego© sets that have the same number, to avoid conflicts, the common practice is to add ".set" as a suffix to the set number. Do not use a numerical suffix (like ".1"), otherwise this suffix will be interpreted as a color (see below for more details), and the color information is irrelevant for a set. Moreover Peeron and Bricklink also use a dash followed by a number to differentiate parts from set, and also because different set produced over the years may have the same number. So it is recommanded to use this suffix and use the same numbers as in Peeron or Bricklink.
<SetNumber>.set.gif <SetNumber>.set.xml For example the naming convention for the set #2150 is: 2150-1.set.gif Moreover if you want to split a set in different gif images, you can name them roughly according to what the splitted part represents like: 7945-1.station.gif 7945-1.truck.gif etc... And it would be nice to add an xml file to group them, and which you can name *.set.xml, like: 7945-1.set.xml If you want to make GIFs of the alternative Lego models which can be found in a set, the naming convention should be as follows: 4886-1.set_option_1.gif 4886-1.set_option_2.gif 4886-1.set_option_3.gif etc...
The common standard for naming a LEGO© part is to use the full part number, followed by a dot and then by the color code of the part according to the LDRAW color table, and finally by the extension.
<PartNumber>.<Color>.gif <PartNumber>.<Color>.xml For example the naming convention for a Blue Baseplate 32 x 32 is: 3811.1.gif The LDRAW color table is: 0 Black 28 Dark Tan 134 Pearl Copper 1 Blue 29 Light Purple 135 Pearl Gray 2 Green 33 Trans Blue 137 Pearl Sand Blue 3 Teal 34 Trans Green 142 Pearl Gold 4 Red 36 Trans Red 151 Light Stone 5 Dark Pink 37 Trans Violet 256 Rubber Black 6 Brown 40 Trans Gray 272 Dark Blue 7 Gray 41 Trans Light Cyan 273 Rubber Blue 8 Dark Gray 42 Trans Flu Lime 288 Dark Green 9 Light Blue 45 Trans Pink 313 Maersk Blue 10 Bright Green 46 Trans Yellow 320 Dark Red 11 Turquiose 47 Clear 324 Rubber Red 12 Light Red 57 Trans Flu Orange 334 Chrome Gold 13 Pink 69 Bright Purple 335 Sand Red 14 Yellow 70 Reddish Brown 366 Earth Orange 15 White 71 Stone Gray 373 Sand Violet 17 Light Green 72 Dark Stone Gray 375 Rubber Gray 18 Light Yellow 73 Medium Blue 378 Sand Green 19 Tan 74 Medium Green 379 Sand Blue 20 Light Violet 77 Paradisa Pink 383 Chrome Silver 21 Phosphor White 78 Light Flesh 462 Light Orange 22 Violet 79 Translucent White 484 Dark Orange 23 Violet Blue 85 Medium Lilac 494 Electric Contact 25 Orange 86 Dark Flesh 503 Light Gray 26 Magenta 89 Royal Blue 511 Rubber White 27 Lime 92 Flesh
The file name of the group parts (parts made from other parts arranged in a specific, predifined layout) should start with any name describing the group followed by a dot and then the word "group" and finally by the extension. The group parts never have gif file, only xml files. If you want to make a group which actually represents a set (for example a set including many buildings in a predifined layout), use the "set" naming convention instead (see above).
<GroupName>.group.xml For example the naming convention for a flex track can be: flex.group.xml