If I were in you I'd write some software tool (in Matlab, C, whatever) to convert the image into a data format suitable for your final application.
For example, suppose that your FPGA is going to take raw data from an ADC.
First you convert a JPG into a text (or binary) file using Matlab.
Then, in simulation, you write a testbench that load the input file and feed the data to the device under test.
Later, with the real FPGA, you will pass the same file to your test equipment (e.g. a NI GPIO board) to emulate your ADC - if you really need this verification step.
For other applications you may need to packetize the data, build a protocol layer, etc...