Basicaly i had this problem myself, and this is an easy and fast fix for that.
if you recently upgraded to latest revisions , you might encountered that some of your vendors or npcs , appear as small blue and white boxes, now thats because new revisions cannot have 1 in the following collumns that you see in my SQL fix
Code:
UPDATE `creature_names` SET male_displayid = 10913 WHERE `entry` BETWEEN '50000' and '50048';
10913 is the displayid , so change that to whatever displayid are of your vendors
Code:
UPDATE `creature_names` SET female_displayid = 0 WHERE `entry` BETWEEN '50000' and '50048';
Code:
UPDATE `creature_names` SET male_displayid2 = 0 WHERE `entry` BETWEEN '50000' and '50048';
Code:
UPDATE `creature_names` SET female_displayid2 = 0 WHERE `entry` BETWEEN '50000' and '50048';
- 50000 and 50046 is the spawn ids for my vendors - so change the values in orange according to your database.