You haven't mentioned what settings you are using on jpg2dcm. Another problem is that there are multiple JPEG versions. If these are JPEG-LS or JPEG_LOSSLESS, the transfer syntax of JPEG baseline is not appropriate. Look at the Javadoc for org.dcm4che2.data.UID and you will several entries for JPEG. If you are using JPEG-LS or JPEG-LOSSLESS, you have to use the correct transfer syntax. However, the DCM4CHEE server may not support these formats.
If you are storing a JPEG-LS or JPEG-LOSSLESS as JPEG Baseline, you could errors like those shown above because the system will be using the wrong codec. Try storing them as uncompressed images. (If you are using a PACS system as the original source, your PACS viewer should be able to decompress the images.)
If you can open the image file using a web browser, the images are probably JPEG baseline. If you can't and have to use a PACS viewer, then they are probably other formats.
I realize that this may be a little confusing. JPEG, JPEG-LS, and JPEG-LOSSLESS are three different compression schemes. The transfer syntax must represent the actual compression scheme. JPEG-LS and JPEG-LOSSLESS may not be supported on your DCM4CHEE server.