Standard addition calibration method can be a solution for ICP-OES, but I would also try ET-AAS with matrix modifiers.

You can try the method described by Oregioni and Aston (1984): The determination of selected trace metals in marine sediments by (Flameless/Flam-Atomic Absorption Spectrophotometry). IAEA Monaco laboratory Internal Report, 75p

Probably your ICP-OES has an accesory for high solids, however you would try standard addition

When dealing with high salt contents, electrochemical methods can be handy. The electrolyte is contained in the sample, no need for external additions. You will have to do some bibliographical research to check for detection limits. Anodic stripping voltammetry can be used for Pb and Cd, you can vary preconcentration time. Also you may complex the metals and adsorb them on mercury with good performance, you will probably reach lower detection limits. You will need to perform standard addition on each sample.

For high salt solutions there are a number of possibilities two of which have been mentioned.  For AAS with the high salt you will probably have to use some form of background correction such as deutrium lamp or  Smith-Heitfje if available on your instrument.  For ICP there are nebulizers that are designed for high solids.  An internal standard would also be a good idea.  Electrochemical methods can be useful depending on the metals and their oxidation states.  Anodic stripping voltametry can be used for Cu, Pb, Cd, Zn, Tl.  Differential pulse or square wave voltametry can be used for a number of other metals.  The metals could be determined by ion chromatography.  It may also be possible to extract the metals from the high salt solution.  Diethyldithiocarbamate complexes a broad range of metals.  The complexes can be extracted into methy-isobutyl ketone.  This could be analyzed directly by AAS.  Alternatively the metals could be back extracted into an aqueous solution although it would have to be fairly acidic.  One could also use ion exchange chromatography to remove  or reduce the salt content.

In my opinion the best way is to separate salt content (NaCl) by some special resins. The salt content can harm the measuring equipment; specially the neubulizer in ICP.

This Paper may helpful to you

Analysis of Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater using the Nobias-chelate PA1 resin and magnetic sector inductively coupled plasma mass spectrometry (ICP-MS)

Dondra V. Biller ⁎, Kenneth W. Bruland

Department of Ocean Sciences, University of California Santa Cruz, CA 95064, USA

I agree with Sundararajan, that you would need some way of analyte/matrix separation. There are some on-line solution around with chelation that work excellently with seawater. They can also be coupled to ICP-OES. You can also do this off-line which is more labour intensive but less expensive.

When trying to select an analytical method, you should think about how to determine the analyte in that particular matrix. Sampling handling to separate the matrix is extra work, and sometimes hard. If you need to get rid of the salt, this is not your method. Use an electroanalytical method.  The electrolyte (salt) is contained in the sample, no need for external additions.  I would definitely go for it.