JR are pretty responsive in adding file types, but in the interim you can add your own (it has been a while since I did this.....and from memory)
1) Open in Notepad C:\Program Files (x86)\J River\Media Center 17\Data\Default Resources\FileAssociations.xml
2) You may need to modify three parts of this file, eg you could try the following suggestion but you would know better than me what should be added.
Add values to these lines:
<Image>JPEG Image (jpg,jpe,jpeg);GIF Image (gif);BMP Image (bmp);TIFF Image (tif,tiff);PNG Image (png);RAW Image (crw,cr2,nef,mrw,orf,raf,pef,dng,srf,arw,x3f,rw2);Photoshop Image (psd);3D JPEG Image (jps,mpo); Vector Grapic Image (ai,eps) </Image>
<IMGTypes>jpg;jpe;gif;jpeg;bmp;tif;tiff;png;crw;cr2;nef;mrw;orf;raf;pef;dng;srf;arw;x3f;rw2;psd;jps;mpo;ai;eps</IMGTypes>
and add Items Names under the <Audio> section such as
<Item Name="ai">audio/ai</Item>
<Item Name="eps">audio/eps</Item>