Dan, this is something you could probably format in a couple seconds. I've tested this on a folder with a bunch of .jpg and the output is a list in the incorrect format...you are much faster at conversion than I am.
import arcpy
from arcpy import env
env.workspace = r"d:\data"
myList = arcpy.ListRasters("", "jpg")
print(myList)
OutGDB = "C:/_scratch/test.gdb/blah"
as a sample with my data...
print(myList) # gives me
[u'bluefin.JPG', u'char.JPG', u'clams.JPG', u'cod.JPG', u'dungenes.JPG', u'fish.JPG', u'grayling.JPG', u'halibut.JPG', u'herring.JPG', u'octopus1.JPG', u'salmon-chum.JPG', u'salmon-sockeye.JPG', u'skipjack.JPG', u'sole.JPG', u'squid2.JPG', u'trout-lake.JPG', u'trout-rainbow.JPG']
Jay would need"
"bluefin.jpg; char.jpg; clams.jpg; ....."
no "u" , [] or single quotes....separated by semi-colon...and enclused with double quotes. I'm not sure if full path to the data is also needed.