File types which are classified 'image' files are as follows:
(Recommended file types are shown in bold)

aces
avci
avcs
bmp
cgm
dicom-rle
emf
fits
g3fax
​gif
heic
heic-sequence
heif
heif-sequence
hej2k
hsj2
ief
jls
jp2
​jpeg
jph
jphc
jpm
jpx
jxr
jxrA
jxrS
jxsi
jxss
ktx
naplps
​png
prs.btif
prs.pti
pwg-raster
svg+xml
t38
tiff
tiff-fx
vnd.adobe.photoshop
vnd.airzip.accelerator.azv
vnd.cns.inf2
vnd.dece.graphic
vnd.djvu
vnd.dwg
vnd.dxf
vnd.dvb.subtitle
vnd.fastbidsheet
vnd.fpx
vnd.fst
vnd.fujixerox.edmics-mmr
vnd.fujixerox.edmics-rlc
vnd.globalgraphics.pgb
vnd.microsoft.icon
vnd.mix
vnd.ms-modi
vnd.mozilla.apng
vnd.net-fpx
vnd.radiance
vnd.sealed.png
vnd.sealedmedia.softseal.gif
vnd.sealedmedia.softseal.jpg
vnd.svf
vnd.tencent.tap
vnd.valve.source.texture
vnd.wap.wbmp
vnd.xiff
vnd.zbrush.pcx
wmf
x-emf -DEPRECATED in favor of image/emf
x-wmf -DEPRECATED in favor of image/wmf

​

NOTE: Although this list is extensive and all of the above can be uploaded, the viewer's device may not support all of these file types, which is why we recommend using the file types highlighted in bold.